miss inform of contract

For the last 8 years iv been dealing with mtn and recently I was called to renew my contract which I went and did I was not told my data was uncapped I been paying R2900 a month after I signed my bill is coming to more then R4500 a month which is a lot of money I called the call centre and they told me only the store can help me and when I called the store they unhelpful the person who I took the contract with was razia she never explained to me anything finally spoke to the manager razak which was no help as well as telling me can't help me and that I should just accept the bill were do I go from here as a loyal customer