I am currently 3 years into a dmp . Two of my debts are with Marks & Spencer one they have defaulted and are charging no interest the other is now marked up to date and they are charging me 24.9 % interest. Initially both were interest free but after 6 months they reinstated interest on 1 account. If I write to them to ask how they could treat 2 accounts belonging to the same person so differently are they likely to start charging interest on the defaulted account? Should I let sleeping dogs lie?