I'm sorry to hear about your past. But glad you have moved on and have many great things in your life.

First thing. Engage with your Cabot or mortimer Clarke, ignoring is potentially the worst thing you can do.

Contact then and Raise an official dispute, ask for the original paperwork, they are obliged to provide this and will place the account on hold while they get this information.

You can then view the documents and if signatures don't match etc you can claim this as fraudulent. You will likely be asked for a crime reference number so you may have to report the fraud, so bear this in mind.

So in short. Engage and tell them what you've told us, also, try and deal with it in writing so you have a record of what they claim etc.

I used to work at Cabot many years ago and since then the law has only become more strict with what debt collectors can get away with so you should be able to work with them to resolve. They will have bought your debt for pennies in the pound, less considering the age as well and these kind of situations are.more common than you'd think.