Remove the block in my account

Good day. My acc was on debt review last and finished paying the account last, which I ended up over paying the account with over R600. I have been recieving monthly statement reflecting the amount due to me. I tried going to the store to make a purchase, when I got there I was told my account is blocked. I spent over an hour in the store trying to find the error. Only to be told it has a block code M, I was sent to pillar to post. Called even their collections department which they said RCS needs to remove the block because it shows the account is up to date. Please help I need to remove the block and least get my money back. I feel like the organisation is confused at the moment since they moved to RCS