Sales agents give misleading information

I am struggling tonget out of this contract with Vodacom. When the term ends they offer a new cheaper deal, but when the statement comes the deal is nit what we agreed on. I am calling them to fix it, they send me from pillar to post. I as for the recording of a call, they wont give me. The last agent sent me to the shop, the shop says they cannot help me. I feel trapped and unheard. All I wanted was to convert to prepaid, they convinced me to get a cheaper deal, now I am back to paying high amounts. Its exhausting.