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 19 May 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 8-week clock has not started.
Under Ofcom rules, Three has up to 8 weeks to resolve a formal complaint. During this period, follow up by phone or via the complaints page if you do not hear back. Keep a written log of every interaction. Note that Ofcom has signalled it will reduce this period to 6 weeks for complaints raised on or after 8 April 2026, so check the latest Ofcom rules at the time of your complaint.
If 8 weeks pass with no resolution, or if Three sends you a "deadlock" letter, you can refer the complaint free of charge to CISAS (Communication & Internet Services Adjudication Scheme). CISAS is independent of Three and its decision is binding on Three if you accept it. Note: Three uses CISAS, not Ombudsman Services. Apply via cisas.org.uk.
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 8-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 Ombudsman Services. Sending your case to the wrong scheme delays everything.
Mention deadlock
A "deadlock" letter from Three lets you go to CISAS before the 8 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 Ombudsman Services. Always check Ofcom’s current list before sending a case, scheme memberships do change occasionally.
Currently up to 8 weeks from the date a formal complaint is logged. Ofcom announced in 2025 that this will reduce to 6 weeks for complaints raised on or after 8 April 2026, so the exact deadline depends on when your complaint was opened. If Three issues a "deadlock" letter before either deadline, you can go to CISAS immediately.
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 remain separate trading entities for now even though they share a holding group. Complaints about a Three mobile or broadband contract stay with Three and route to CISAS. Complaints about a Vodafone contract route to Vodafone’s ADR scheme (currently Ombudsman Services). Use the brand on your bill as the deciding factor.
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