Poor customer service from DMC repayment

I have requested the proof of my payment from them and they told me they will send it to me I'm still waiting 2 months now but when they asked me to repay another account of mine they were quick to send me the banking details of them to repay them I'm now at this point I must make another payment at the end of the month which I have doubts about repaying them just because of their bad service quick to get something from you but very slow to respond to your demands