Worst service ever

Worst service ever, I called in asking for a settlement amount which indeed I received... I then made payment but only to find out I've overpaid them. I then was instructed to send relevant documents which I did. I received an email saying my proof of residence was invalid and needed to send another one. A diffrent proof of residence was resent and a week later, I received same email saying proo of residence was also invalid. I've been trying to call them to get this resolved and have been put on hold until the phone disconnects. This is rather quiet frustrating and time consuming.