Credit on my account - No feedback after more than 5 calls to call centre

I have called the DSTV callcentre more than 5 times so far about the same thing. They have been billing me extra by R400 on my account since 2015. They acknowledge this and promised to credit my account but they are not doing so. Everytime I call they can see notes on this query but never have they communicated back either via a call or mail.

This is poor service whcih I have raised with them but no action on their part!!!!