I agree with the idea of sending the debt collection people a copy of your mobile phone bill showing your name and the telephone number. Don't show them the address though, as they'll likely use that against you!
I caveat with the following - I am not a solicitor!
ChatGPT has come up with the following Cease and Desist letter:
"Dear DebtCollector
I am writing to formally request that you cease and desist all collection activities regarding the alleged debt associated with my telephone number (07XXX XXXXXX), as this debt does not belong to me.
I have received numerous communications from your company regarding an account that you claim is owed by Katie Ellis, but I am not that person and have no connection to this debt.
I provide proof that I am not Katie Ellis with the enclosed copy of my mobile phone bill, showing the telephone number you are using to try and contact Ms Ellis and my name.
Under the UK Consumer Credit Act and the guidance set forth by the Financial Conduct Authority, I request that you stop all collection efforts and refrain from any further contact with me regarding this matter.
Please conduct a thorough investigation and confirm in writing that you have removed my details from your records and that no further action will be taken against me.
Thank you for your prompt attention in this matter. I look forward to your confirmation.
If you do not cease and desist your collection activities, I will have no option but to appoint a solicitor to deal with your harassment.
Yours faithfully
Cocoapuffpuff
cocoapuffpuffatgooglemail.com"
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Many years ago I answered an unrecognised number on my phone and this bloke just went "Katie?". I said, "no, sorry - I think you have the wrong number"
He said "no I ain't", so I said "yes you have", so he said "no, I ain't", so I said "well, I'm not Katie, so clearly you have" and he went mental at me! I hung up on him and he kept trying to call over and over again.
I imagine she gave him a fake number because she never wanted to hear from him again. I wonder why!
Thankfully after not getting through to me again he gave up.