✦ Company complaint letter guide
Three complaint letter: broadband, mobile and billing
Create a structured Three complaint letter for broadband faults, mobile issues, billing disputes, cancellation problems or poor customer service.
Choose the problem
Start with the Three issue that matches your complaint
Telecom complaints need clear service dates, account numbers, fault references and the practical impact.
Broadband outage
Use this when broadband or phone service is down, intermittent or repeatedly unstable.
Start this complaint →Slow broadband
Use this when speeds are consistently below what was sold or expected.
Start this complaint →Billing dispute
Use this if charges, direct debits, roaming fees or final bills are disputed.
Start this complaint →Cancellation problem
Use this if cancellation was delayed, ignored or followed by further charges.
Start this complaint →Early termination charge
Use this where an exit fee appears wrong or unfairly applied.
Start this complaint →Poor complaint response
Use this where responses are delayed, inconsistent or do not address the complaint.
Start this complaint →Complaint route
How a telecom complaint should progress
Complain to the provider first and keep evidence of faults, charges and customer service contact.
Complain to the provider first
Give account details, fault references, dates, charges and the outcome requested.
Ask for deadlock if stuck
If the provider will not resolve the issue, ask for its final position or deadlock letter.
Escalate if unresolved
If unresolved after the relevant waiting period or deadlock, use the provider’s ADR route if the complaint is in scope.
Check the provider page because telecom ADR scheme membership can vary.
Evidence checklist
What to include for each Three complaint type
Use the checklist to make the letter specific enough for the company to investigate and respond.
| Complaint type | Evidence to include | Likely outcome to request |
|---|---|---|
| Broadband outage | Account number, outage dates, speed tests, fault references and screenshots. | Service fix, bill credit or compensation where appropriate. |
| Slow broadband | Speed tests, router checks, contract details and fault reports. | Technical review, service fix or cancellation route. |
| Billing dispute | Bills, tariff details, payment history and previous replies. | Corrected bill, refund or account credit. |
| Cancellation problem | Cancellation request, notice date, bills and chat transcripts. | Contract correction, refund and confirmation of closure. |
| Early termination charge | Contract, notice, final bill and fee calculation. | Fee review, correction or refund. |
| Poor complaint response | Complaint reference, response dates and unresolved points. | Substantive response, deadlock or escalation. |
- Evidence to include
- Account number, outage dates, speed tests, fault references and screenshots.
- Likely outcome to request
- Service fix, bill credit or compensation where appropriate.
- Evidence to include
- Speed tests, router checks, contract details and fault reports.
- Likely outcome to request
- Technical review, service fix or cancellation route.
- Evidence to include
- Bills, tariff details, payment history and previous replies.
- Likely outcome to request
- Corrected bill, refund or account credit.
- Evidence to include
- Cancellation request, notice date, bills and chat transcripts.
- Likely outcome to request
- Contract correction, refund and confirmation of closure.
- Evidence to include
- Contract, notice, final bill and fee calculation.
- Likely outcome to request
- Fee review, correction or refund.
- Evidence to include
- Complaint reference, response dates and unresolved points.
- Likely outcome to request
- Substantive response, deadlock or escalation.
Outcome request
What you can ask Three to do
The strongest complaint letters state the practical result you want, not just what went wrong.
Use this page to prepare a clear, firm complaint to Three. The aim is to summarise what happened, what you want them to do, and the evidence that supports your position.
What this letter should achieve
- State the problem with dates and reference numbers.
- Explain the impact (financial, practical, or time lost) in concrete terms.
- Request a specific remedy (refund, correction, apology, compensation, or service fix).
- Set a clear deadline for response and next steps if unresolved.
Common issues people complain about (Telecoms)
Typical themes include: Billing dispute, Service outage, Contract / cancellation, Poor customer service. Keep your letter focused on the main issue and avoid adding unrelated grievances.
What to include
Evidence: Account number, contract dates, bills, fault logs/screenshots, and correspondence.
- Key dates in order (what happened first, next, and most recently).
- Any reference numbers (booking/order/account/claim IDs).
- What you have already tried (calls, chats, emails) and the outcome.
What to ask for
- Be specific: the amount, the action required, or the correction you want.
- If your losses are quantifiable, itemise them briefly.
- If you want an apology or assurance, say so explicitly.
Escalation and timeframes
Expected wait: Allow the provider a reasonable time to respond; if unresolved, ADR routes are typically available after deadlock or set time limits.
Escalation route: Alternative Dispute Resolution (ADR) scheme used by the provider (e.g., Ombudsman Services or CISAS). If you reach deadlock or do not receive a meaningful response, you can escalate via the appropriate dispute route for the sector.
Practical tips
- Keep it factual and polite; avoid insults or speculation about motives.
- Use short paragraphs and bullet points for dates and costs.
- Save copies of everything you send and receive.
Three complaint FAQs
How long should I give Three to respond?
What should I attach as evidence?
What if they do not reply or refuse to resolve it?
How do I structure a complaint about: Billing dispute?
How do I structure a complaint about: Service outage?
Related guidance
Useful next pages
Use these pages to compare complaint routes, prepare evidence and start a letter for another company.
Mobile and broadband complaints
Browse other companies and complaint routes in this sector.
Open sector → GuideHow to Escalate a Complaint to the Ombudsman: a UK Step-by-Step Guide
Step-by-step guide on how to escalate a complaint to the ombudsman in the UK. Understand the process clearly and effectively.
Read guide → GuideThe 2026 UK Consumer Complaint Index
Explore the 2026 UK consumer complaint index for insights into complaint trends across sectors. Reliable data to inform your rights and actions.
Read guide → CompaniesFind another company
Search by sector or company and start a tailored complaint letter.
Browse companies → ToolComplaint letter generator
Start from scratch if you do not need a company-specific page.
Open generator →More routes
More useful pages for Three complaints
Compare similar company pages and read issue-specific guidance before you create your letter.
BT complaints
Open another mobile and broadband complaint route with company details preloaded.
Open company → Same sectorEE complaints
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Open company → Same sectoriD Mobile complaints
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Open company → GuideWhy most UK refund complaints fail and how to fix them (2026 guide)
Company refusing a refund? Learn why refund complaints fail, what UK law says, and how to structure a legally framed refund complaint letter that gets results.
Read guide → GuideComplaint Letter for Faulty Goods After 30 Days (UK)
Retailer refusing help with faulty goods after 30 days? Learn your rights under UK consumer law and how to write a structured complaint letter that gets a response.
Read guide →