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The UK Phone Bill Autopsy: A Line-By-Line Walkthrough of What You Are Actually Paying For

#voip #cost #uk #billing

Honestly, I have been doing these "bill autopsies" for about 4 years and the thing that still surprises me is that most UK business owners have never actually read their phone bill. Just signed it on direct debit years ago and never looked back. So let me walk through a real one.

This is an anonymised real invoice from a 22-person estate agency in Reading, December 2025. They thought they were paying "about £600 a month". Actual figure: £1,247.

The invoice, line by line 

Supplier: BT Business
Account: 22 extensions, 3 sites, ISDN2e × 4
Period: 1-31 December 2025

Line rental and channel fees
  ISDN2e (8 channels) × 4              £312.00
  Additional DDI range (100 numbers)   £ 28.00
  Mainsite-factory fibre failover       £ 89.00
                                       --------
                                       £429.00
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First surprise: 32 channels of ISDN. Concurrent calls in peak hour: 11. They had been paying for 21 channels of pure air for 9 years. Line rental alone: £3,756 / year wasted.

Calls
  UK local (01/02)         2,184 mins  £ 54.60
  UK national (03/0345/0800 receiving) 318 mins £ 15.90
  UK mobile                1,126 mins  £101.34
  International            14 mins     £  4.20
  Premium (0845/0870 receiving fees)   £ 38.00
                                       --------
                                       £214.04
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Mobile minutes at £0.09/min. At 2026 VoIP rates this should be £0.015/min. Overpayment on mobile alone: £85/mo.

The 0845 receiving fees are the sneaky one. Everyone thinks 0845 is free. It is free for the caller. The recipient pays to receive calls to 0845 numbers, at typically £0.03-0.08/min. This invoice has £38 of that and the owner had no idea.

Features and services
  Hunt group (main)                    £ 28.00
  Hunt group (sales)                   £ 28.00
  Call divert (18 numbers)             £ 45.00
  Call divert (mobile twin, 14 users)  £126.00
  Voicemail-to-email (14 users)        £ 70.00
  Auto-attendant (1 config)            £ 45.00
  Call recording (4 users only)        £ 76.00
                                       --------
                                       £418.00
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Every single one of these features comes included on any modern VoIP plan. They were paying £418/month, £5,016/year, for features that are now commodity. Call recording limited to 4 users (!) because recording is billed per licence.

Mobile twinning platform
  14 × twinned mobile numbers          £126.00
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This line made me laugh out loud when I first saw it. They were paying £9/month per user for "mobile twinning" which is literally just forwarding the office number to a mobile. Any VoIP mobile app does this for free. £1,512/year for a feature that is part of the basic plan elsewhere.

Maintenance and support
  BT Care 2 (8×5 NBD)                  £ 48.00
                                       --------
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£48/mo for next-business-day fixes. Their last fault took 11 days to resolve. They were paying for a support SLA they could not actually get.

Total before VAT                      £1,039.04
VAT at 20%                             £207.81
                                       --------
Grand total                          £1,246.85
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What they are paying now

Item Before Now
Per user (22 users × £24) - £528.00
Hardware (rental) 0 £44.00
Number porting (first 3 months only) - £0 (included)
VAT £207.81 £114.40
Total £1,246.85 £686.40

Annual saving: £6,725. Payback on new IP phones (£1,200 capex): 2.1 months.

The invoice features they did not realise were unused

  • 2 hunt groups, but they only needed 1 (the "sales" hunt group had not routed a call in 18 months)
  • Call recording on 4 users while the other 18 had no recording — no policy, just historical billing
  • Mobile twinning for 14 users but only 7 actually used it

Scrub your invoice. Write down what each line is supposed to do. Ask which ones you actually use. You will find £150-400/mo of dead features on most UK phone bills older than 3 years.

How to do your own autopsy in 30 minutes

  1. Get the last 3 invoices from your provider
  2. Print them. Yes, paper. You want to annotate.
  3. For every line, answer: what does this do, do we use it, when was it last used
  4. Highlight any line where the answer to "do we use it" is "I think so?"
  5. Add up the "not sure" lines — that is your minimum monthly saving from switching

I have yet to do this with a UK business and not find at least £80/month of nonsense. The record so far is £1,120/month on a 45-person law firm's invoice in Leeds.

DialPhone will do a free bill autopsy for any UK business. Send us your last invoice, we send back a line-by-line breakdown and the real monthly figure if you moved.

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