C-Fiber premiums increases after contract is signed.

I have signed a contract for fiber with CellC in February 2020 for an amount of R749 per month. They could only manage to uphold their side of the contract for a mere 4 months. They decided to send messages to their newly signed customers (including myself) informing us of a tariff increase. There were no mention of this anywhere in the contract, and no mention of this were ever made. The lady that assisted me with the installation also confirmed this. I immediately sent an email to their customer support, to express my disappointment, shock and dissatisfaction and asked for an explanation. I received no answer. I again asked for a response 8 days later, and still received no response apart from a customer satisfaction survey. I rated them poorly as I have not received any explanation or way forward. Still I received nothing after this. Today I have noted that my bank account have been debited by CellC to the amount of R879. An increase of R130 on my monthly premium after only 4 months. So after you sign a contract with them for a certain amount, they feel entitled to increase your tariff at ANY time, for ANY amount they wish?!? How is this normal? When is the next increase and by how much then? I have still received no response from CellC. I will continue on as many social media platforms as possible to warn as many people as possible to NEVER sign a contract with CellC, until my tariff have been rectified to the amount I have signed for (R749), or I am offered the opportunity to cancel without penalty in order to sign up to a better service provider.