Contract renewal without consent of client

I took a month to month contract with cell C for data only 30GB around May 2021 now when i want cancel it am told that the contract was changed to fixed contract of 24 months from 1st November 2021 to December 2023 without my consent.... The consultant was very rude to tell me that they didn't need my permission/ consent to change the terms..... Apparently they did this to every customer who was on the 30Gb data......