Unauthorized debits

Took a loan with Capfin November 2014 and first instalment was December 2014 to end May 2015, now in May I thought I have settled the account and called the call centre for settlement letter only to be advised I had a previous missed payment, I agreed to settle and advised them it will be cash payment as i'm closing the account and moving to another bank then the consultant said its fine and we agreed on the date, to my surprise they submitted a debit order the same month I called to change the banking details which caused me bank charges, let it go and the following month as agreed paid cash the missed payment but I still got sms's that I haven't paid and I paid even prior to my debit date called them they said sorry, then I requested a settlement letter then I was told there is an outstanding amount which are arrears, which initially when I called for the first settlement letter I was not advised of and they are still sending debits to the previous account and i'm being billed for returned debits, and they said there is nothing they can do about those, I settled those arrears but they still billed me again, and they promised a refund which im still waiting and its been days