Cabot chasing debt - help needed

[Guest]

I had a joint business bank account with HSBC with my ex husband,* Our business went bankrupt at a time at which we had an unsecured overdraft with HSBC.* Shortly after the bankruptcy the debt was sold to a debt collection agency who only contacted my ex husband who agreed to small monthly installments which he has been continuing to pay. I have been paying the my ex husband directly to cover my share of this. The debt was later sold on to Cabot who for several years have continued to only deal with my ex husband.* Out of the blue I received a letter today from Cabot saying that they require me to make repayments, strangely my ex received the exact same letter today and when he rang them to say that he had already got a repayment arrangement with them they agreed with him and said that the letter must have been sent out by mistake.* What do I do? Do I contact Cobat? Does the fact that they have agreed repayments with my ex cover the debt repayment?