Over payment. Account settled

My virgin active account was handed over to MBD. I settled the account last week. They debited my bank account twice. As a result I over payed on my balance. I called them on the 26th to try and sort it out. The agent I spoke to first time said she would ask her supervisor how I will be refunded as she can see I have settled and I have over payed. She promised to get back to me. That was on Thursday. She didn't get back to me. I called on Friday, spoke to another agent who also promised to call me back, but he did not. Today is Monday, I called AGAIN. Still no solution. I'm also still waiting for my payed up in full letter. I can never get any answers from these consultants. I am put through different departments and they ALL promise to call me back but don't. I want MY money!