Helping themselves to my money.

Settled my account 29th of May. Still got debited in June and July been requesting for a refund, but they send me from pillar to post. Making me send and resend the same documents over and over again. They don't get back to you when they say they will and refusing to give me a paid-up letter. Saying my account was only paid up on the 20th July cos that was the last payment received... irrespective of the fact that it was a wrongful debit.