Terms of contract do not matter

I have had a contract with Telkom for the longest time and this year on February 2024 I renewed my account for a plan For 120 GB day and night for the amount of R249 which I thought I could afford but recently just within 3 months of the contract the billing went up by R20 and it was now I have to pay R269 just like that so is this how Telkom works if they feel like increasing they just going to increase without anyones consent of the customer whst if I can afford. I plan to cancel the contract plus their service is poor and no signal most of the time. Please beware that Telkom increase tariffs anytime.