Hello, my name is Jim and I am a qualified lawyer happy to help you today.
You can allege breach of contract against TalkTalk (you have consumer rights here which have been infringed in my view).
Given the circumstances of your case I recommend that you make a formal complaint against TalkTalk and if that does not resolve the matter ask them for a final response letter (a "deadlock" letter).
You can make the complaint with TalkTalk here:
Once you have the deadlock letter the next step would be to escalate this to the adjudication scheme (CISAS) - they will investigate and liaise with TalkTalk which would hopefully result in a refund of any monies paid. They can also order the phone company to make a financial award if they have acted badly.
The service is covered by the Consumer Rights Act 2015 so you have a right to expect a reasonable service - if they do not provide that then the regulator will step in but it also means you can sue for any damages or losses incurred as a result of TalkTalk's conduct.
You can escalate to the adjudicator here : https://www.cedr.com/consumer/cisas
If you have lost any money then you could sue TalkTalk but the court may consider that to be premature if you do not go through CISAS first of all.
You can sue for your losses via the http://www.moneyclaim.gov.uk website which is easy to use and no lawyer would be required.
I hope this helps - if you can please accept the answer and give me a 5 star rating (there should be a button at the top of your screen to do this), I can answer follow up Q&A's at no extra charge and Just Answer will credit me for helping you today.