Three sits in the worst quartile of Ofcom’s Q4 2025 complaints table for both broadband and mobile, so knowing how to escalate properly matters. This page walks you through the five steps from a first phone call to CISAS, Three’s alternative-dispute-resolution scheme, plus when Ofcom automatic compensation applies.
At a glance
At a glance
Complaints
Updated 15 September 2026
Step by step
Follow these in order. Most complaints resolve at step 1 or 2; only escalate further if Three does not put it right.
From a Three handset dial 333, free of charge. From any other phone dial 0333 338 1001. Explain the problem clearly: what is broken, when it started, and what outcome you want. Most issues are resolved at this stage. Always note down the date, time, agent name and a one-line summary of what was agreed.
If the first call does not solve it, explicitly ask the agent to log a formal complaint and give you a complaint reference. Without that reference, your call is just a service enquiry and the 6-week clock has not started.
Three has 6 weeks to resolve a formal complaint before you can take it outside the company. This was 8 weeks until 8 April 2026, when the threshold was cut, so any guide written before that date, including Three’s own older PDFs, still quotes the longer figure. Three says it answers most complaints within 7 working days. During the window, follow up by phone or via the complaints page if you do not hear back, and keep a written log of every interaction. One exception keeps the old clock: a complaint about a device payment plan is a financial-services matter, runs to 8 weeks and goes to the Financial Ombudsman Service rather than CISAS.
If 6 weeks pass with no resolution, or if Three sends you a "deadlock" letter sooner, you can refer the complaint free of charge to CISAS (Communication & Internet Services Adjudication Scheme, run by CEDR). CISAS is independent of Three and its decision is binding on Three if you accept it. Three uses CISAS, not the Communications Ombudsman. Apply via cedr-assist.com/consumer/cisas, call 020 7520 3814 or write to CISAS, 100 St Paul’s Churchyard, London EC4M 8BU.
For broadband and home phone faults that take longer than 2 working days to fix, missed engineer appointments, or delayed start dates, Three (like all big UK providers) is signed up to Ofcom’s automatic compensation scheme. Credit lands on your bill automatically; you do not have to ask. Current rates are around £9.76 per day of total loss of service. Full rules on the Ofcom site.
Tips that make CISAS easier
CISAS is an adjudication, not a court. The customer with the better paperwork usually wins. These four habits cost nothing and dramatically improve your odds.
Always get a reference
Without a complaint reference number, the 6-week ADR clock has not started. Insist on one.
Keep a written log
Date, time, agent name, what was promised. Screenshots of chat. PDFs of letters. This is your evidence at CISAS.
Use the right ADR
Three uses CISAS, not the Communications Ombudsman. Sending your case to the wrong scheme delays everything.
Mention deadlock
A "deadlock" letter from Three lets you go to CISAS before the 6 weeks are up. Ask for one if no progress.
FAQ
Three is a member of CISAS, the Communication & Internet Services Adjudication Scheme, run by CEDR (Centre for Effective Dispute Resolution). CISAS is one of the two Ofcom-approved telecoms ADR schemes (the other is the Communications Ombudsman, used by BT among others). Three does not use the Communications Ombudsman. Always check Ofcom’s current list before sending a case, scheme memberships do change occasionally.
6 weeks from the date a formal complaint is logged. The threshold was 8 weeks until 8 April 2026, when it was cut, so a complaint opened today runs on the shorter clock and any advice telling you to wait two months is out of date. Three itself aims to answer most complaints within 7 working days. If Three issues a "deadlock" letter before the 6 weeks are up, you can go to CISAS immediately. The one exception is a complaint about a device payment plan, which keeps the 8-week window and goes to the Financial Ombudsman Service instead.
No. CISAS is free to you as the customer. Three pays the case fees and the adjudicator’s costs regardless of the outcome. You do not need a lawyer; the process is paper-based and you submit your evidence (complaint reference, written log, screenshots, bills) through the CISAS online form.
Only for specific broadband and home-phone problems: total loss of service not fixed within 2 working days, missed engineer appointments with less than 24 hours notice, and delayed activation of a new line. Mobile network issues, slow speeds, and individual call quality are not covered. When you do qualify, Three is required to credit your bill automatically, you do not have to claim it.
Three and Vodafone UK still bill as separate consumer brands even though VodafoneThree is one group, so the brand printed on your bill decides where the complaint goes. The practical answer is that it makes no difference to the ADR scheme: both Three and Vodafone use CISAS, so a case rejected by one brand’s complaints team does not have to be re-routed to a different adjudicator. Where it does matter is business accounts, since Vodafone is now the sole brand for VodafoneThree business customers and Three Business accounts are migrating across. Complain to whichever brand takes your money, and quote the account number from that bill.
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