Hi I have had a letter from arrow global chasing a catalogue debt, I think they have had this debt a while now, I checked my credit report and it said default balance £2300, current balance £2036, their letter says I owe £2700!! How should I proceed with this, do debt collectors charge interest on balances I have had another one off arrow different catalogue, smaller amount, but that one matches the current balance on my credit report, why have they added £700 to it? What should I send to arrow?