There is a CCJ which will have been for you to pay at a certain amount per month. You have been paying that amount or more without fail. Provided you go on doing so until all the debt has been paid off there is nothing the creditor (or the new owner of the debt) can do by themselves. They cannot force you to pay more. To do so they would have to get the Court to change the terms of the CCJ. I don't think they have the right to apply to Court to do this (but am not certain). If they can, and do so, you will have the opportunity to give the Court your financial details to help them decide whether the payments should change.