Unfair contract cost increase

My mind just can not comprehend the way Telkom conducts business. I have a contract with Telkom for some years now and never really had issues. But then the calls started, clearly from a call center contracted by Telkom to harass their customers. Doesn't matter how many times I told them I don't need any changes, they just keep on calling even on my DATA Only SIM. Then with no warning my contract cost went up with 25.32% Telkom is a COMMUNICATIONS company but have no clue how to communicate with their customers.... SHOCKING to say the least. This needs to be rectified immediately