Cancelling a contract

Good Day.

I am looking for an assistant with regards to cancelling my month to month contract with Cell C that I took in 2021 May. The contract was on a month to month bases, meaning I could cancel it at any time, but give Cell c a 20 days notice of cancellation. To my surprise that they have change the T&Cs in 2021 November to a full 24 months contract.

They claim they have sent a communication of this change however I did not get any notification.

I was doing the cancellation via contact centre 084143.

I am cancelling this contract due to inaffordability.

Kindly assist