Bad customer service at Cell c

I had a contract with cell cell for more than 2years and it was data 10g night 10g during the day and was paying R136 all these years. End of May 2021 this year they start to debiting 320 and I phone them they promise to refund me and I decide to reverse the money because the other money that they took was for another insurance. To cut the story short on the 18 July 2021 they debit 720 and I phone them they told me that my contract has increase from 136 to 320 with out letting me know I ask them to terminate the contract. All I want now want them to close the contract that I hv with them because it was a 2year contract.