Paid up letter realease

Vodacom is ****ming people i had an account with vodacom i asked them to close my account they said they closed after sometime only to find out that they did not close account by that time i found out is blacklisted so i paid all the money i was owing through mbd. Now they don't want to give me a paid up letter, if i ask them they say i must call mbd if i call mbd they say vodacom haven't issued them the letter I'am really not happy with vodacom and mbd very poor service