error in billing

I lost my job in 2014 January my account was handled over to the lawyers in November 2014 i made arrangements to settle the account and the money was debited on 30 november 2014 in december i started calling them for settlement letter i was told to wait for 21 days after 21 days was told to wait the settlement letter will be sent to. Me while waiting for settlement letter i got an email from the lawyers again telling me i owe R1709 am confused how can i owe the money while i instructed them to debit full amount of what am owing after sending them an email asking for clarity they responded telling me that my account is no longer with them they took it back to Fnb please help.