Horrible service

I have been paying dmc for a couple of years for my real people loan account. This year April my account was paid up through a third party but I was given POP to prove that my account is paid up & I forwarded POP to DMC but for 3 months they continue to debit on my account. I tried sending emails & eventually they stopped debiting on my account. I sent another email now requesting my refund & a lady called Bongiwe rep**** & said to me I wont receive my refund until I get a letter from the third party & when I called them they said they have never heard of that before & unfortunately they can't help me because they have given me POP so DMC won't refund me & I'm told there's nothing they can do. My question is where am I supposed to get refund? I'm honestly disgusted by DMC's treatment toward me