upsetting experience

Cell C consultant called me to sell me a 20gig anytime and 20gig night contract I accepted the contract but when they were loading they only loaded 10gig anytime and 10gig night I immediately called them and they keep on referring me to one center to another eventually they decided to listen to the audio when the initial contract was made they acknowledge that they were wrong and they should have given me 20gg not 10gig and they going to credit my account with R299 as I didn't even use they data since it was incorrect, for some reason they never credited me when I called they told me they won't credit since I used 50mb which on prepaid 50mb is around R20 but I paid R300 for their mistake, they even denied that they promise to credit me claiming that they don't find the reference on that, according to my knowledge they record all calls how come they can't find this one, I cancelled that contract immediately luckily it was a month to month.