Charged full service fees for only half the service provided

Struggling to get my credit out of them.

They Charged me for a 20mbps download and 10 mbps upload line but they only set it so I can use 10D/5U, I had to complain a lot of times but struggled to set it right from Cool Ideas to Vodacom. So I should actually get credit because I was charged for full service but only received half the service until I told them Im not going to pay until they fix it.