How to Switch Business Mobile Provider Without Downtime

Last updated: 26th March 2026

Switching your business mobile provider should save you money, improve coverage, or deliver better service — but the fear of downtime, lost numbers, and contractual headaches stops many UK businesses from making the move. The reality is that Ofcom’s switching regulations make the process straightforward, and with the right approach you can migrate your entire fleet of business mobiles to a new network without a single missed call. This guide covers everything you need to know: PAC codes, STAC codes, porting timelines, bulk migration, early termination fees, and how to avoid every common pitfall.

Understanding the Switching Process

Since 2019, Ofcom’s “Text to Switch” regulations have made it significantly easier for consumers and businesses to change mobile provider. The process centres on two types of codes:

PAC Code (Porting Authorisation Code)

A PAC code lets you transfer your existing mobile number to a new provider. When you give a PAC code to your new network, they initiate the port, and once it completes, your old contract is automatically cancelled. The PAC is valid for 30 days from issue.

STAC Code (Service Termination Authorisation Code)

A STAC code cancels your existing contract without transferring your number. Use this if you want a fresh number on your new network. Like a PAC, a STAC is valid for 30 days.

Comparison: PAC vs STAC vs Auto-Switch

Step-by-Step: Switching with a PAC Code

For most businesses, the PAC code route is the right choice — you keep your numbers, and clients never know you switched. Here is the complete process:

Step 1: Check Your Current Contract

Before requesting a PAC code, understand where you stand contractually. Text INFO to 85075 from each phone to receive a free text message showing your contract end date, any early termination charges, and outstanding handset balances. For business accounts with multiple lines, your account manager or the provider’s business portal can supply this information in bulk.

Step 2: Request PAC Codes

Text PAC to 65075 from each mobile number you want to port. Your current provider must respond within one minute with the PAC code and any applicable termination charges. For business accounts managing many lines, you can request PAC codes in bulk via your provider’s business team or online portal — they are required by Ofcom to supply them within one working day.

Step 3: Choose Your New Provider and Plan

Select your new business mobile provider and the plans you want. This is where working with an independent provider like Connection Technologies pays off — we compare tariffs across EE, O2, Three, and Vodafone and handle the entire migration for you.

Step 4: Give PAC Codes to Your New Provider

Provide each PAC code to your new network. They will schedule the port — typically for the next working day. You can request a specific porting date if you need to coordinate the switch across your team.

Step 5: Keep Your Old SIM Active Until the Port Completes

Do not cancel your old contract separately and do not remove your old SIM card. The port process automatically cancels your old line. Keep the old SIM in the phone until you receive confirmation that the port is complete, or until you see your new network name appear on screen.

Step 6: Insert New SIM (or Activate eSIM) and Test

Once you have confirmation of a successful port, insert your new SIM card (or activate your new eSIM). Make a test call, send a test text, and confirm mobile data is working. Your number will now be active on the new network.

Bulk Number Porting for Business Fleets

Switching one phone is easy. Switching 20, 50, or 200 at once requires coordination. Here is how to manage a bulk migration:

Staggered vs Big-Bang Migration

You have two approaches: port all numbers simultaneously on a single date, or stagger the migration over several days. A big-bang approach minimises the overall transition period but concentrates risk — if something goes wrong, it affects everyone. Staggered migration lets you iron out issues on a small batch before rolling out to the full fleet.

For businesses where all employees perform similar roles (e.g., a delivery fleet or a sales team), a big-bang approach on a quiet day (such as a Sunday morning) often works well. For businesses with mixed roles and dependencies, a staggered approach by department is safer.

Porting Coordination Checklist

1. Compile a spreadsheet of all numbers to port, including the associated employee name, current network, handset model, and PAC code.
2. Confirm eSIM or physical SIM requirements for each device.
3. Pre-configure new SIMs/eSIM QR codes so they are ready to activate immediately after porting.
4. Communicate the porting schedule to all staff in advance — explain that there will be a brief period (typically 2–4 hours) when calls may not connect.
5. Set up call diverts on landlines or Teams/Zoom as a temporary fallback during the porting window.
6. Test one or two numbers first before proceeding with the full batch.

Early Termination Fees by Network

If you are switching before your contract ends, your current provider may charge an early termination fee (ETF). The table below shows how each major UK network calculates these fees:

The key point for businesses: the early termination fee typically covers the remaining airtime charges, while any outstanding handset finance balance must always be paid in full. If your phones are on a separate device plan (as is standard since Ofcom’s 2020 regulations), settling the device balance does not affect your ability to switch airtime provider.

Avoiding Downtime During the Switch

The biggest concern for any business switching mobile provider is missed calls. Here are proven strategies to minimise or eliminate downtime:

Schedule the Port for Off-Peak Hours

Most networks process port requests between 9am and 5pm on working days, with the actual switch happening in a 2–4 hour window. Schedule your port for a day and time when call volumes are lowest — early morning, Friday afternoon, or during a known quiet period for your industry.

Set Up Temporary Call Forwarding

Before the port begins, set up call forwarding on your old SIM to a landline, Teams number, or colleague’s mobile. This way, any calls that arrive during the brief porting window will still be answered. Remove the forwarding once the port is confirmed complete.

Use Dual SIM to Overlap

If your handsets support dual SIM (physical SIM + eSIM), you can activate your new line before the old one ports. Run both lines simultaneously for a day, then initiate the port once you have confirmed the new line works. This provides a safety net — if anything goes wrong with the port, the old line is still active.

Notify Key Contacts

For critical business relationships, proactively inform key clients and partners that you are switching providers and there may be a brief window where calls go to voicemail. Set up a professional voicemail message explaining the situation and promising a prompt callback.

Contract Exit Checklist

Before you commit to switching, work through this checklist to avoid surprises:

1. Check contract end dates — text INFO to 85075 from each line, or review your business portal.
2. Calculate early termination fees — use the table above as a guide, but request exact figures from your current provider.
3. Check outstanding handset balances — these must be paid regardless of switching.
4. Review any bolt-ons or add-ons — international calling packages, data roaming passes, and insurance policies may need to be cancelled separately.
5. Back up device data — while switching provider does not erase your phone, it is good practice to ensure all data is backed up before any SIM change.
6. Confirm new plan coverage — check the new network’s coverage at all your key locations (office, warehouse, employee home postcodes) before committing.
7. Request final bill — your current provider will issue a final bill covering any ETFs, outstanding balances, and pro-rated charges.
8. Unlock handsets if needed — since 2021, all UK networks sell phones unlocked by default. But if you have older devices that are network-locked, request an unlock before switching.

What Happens After You Switch

Once all numbers have been ported and your new SIMs or eSIMs are active, there are a few post-switch tasks to handle:

Update Auto-Pay and Billing

Set up direct debit with your new provider and cancel the old one (though your old provider should stop billing automatically once the port completes). Keep your final bill from the old provider for your records.

Reconfigure Wi-Fi Calling and VoLTE

If you were using Wi-Fi calling on your old network, you may need to re-enable it on the new one. Some network settings are pushed automatically via carrier settings updates, but it is worth checking.

Update MDM Profiles

If your devices are managed by an MDM solution, update the APN and carrier configuration profiles to match your new network. This ensures mobile data, MMS, and any VPN configurations work correctly.

Test All Lines

Do a systematic test of every ported number — inbound call, outbound call, SMS, MMS, and mobile data. For fleets, assign one member of each team to test their line and report back.

Related Help Guides

• ESIM setup guide
• Voicemail setup guide
• Call forwarding guide
• best mobile network in the UK
• business mobile phone plans
• network comparison guide
• cheap business mobile deals
• SIM only deals for business

Related Reading

• PAC Code Guide — Everything You Need to Know
• Best Business Mobile Phone Plans UK
• How to Choose a Business Mobile Provider (2026)

Written by

Karl Hallin

Key Account Manager

Karl is an experienced Key Account Manager with over a decade of expertise in customer service, account management, and team leadership within the telecommunications and financial services sectors.

Key AccountsFleet ManagementTelecoms

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