Unhappy customer - Give customers 30 days notice for tariff increases

I am so unhappy about the treatment received from Cell C Fibre for Home. on 19 May 2021 I received an email informing me of tariff changes, my tariff will increase from R599 to R799 because Vumatel has taken over from SADV and the new tariffs are Vumatel's tariffS. On the email it stated that if me as customer am unhappy with the new tariff I can cancel the contract but need to give at least 20 days notice. The new tariff prices starts on 1 June 2021.

Cell C has given me 11 days notice, but I am expected to give them 20 days notice. How is that fair on the customer? On 20 May 2021 I sent an email to *** to cancel my contract and stated that I would like my contract cancelled on 31 May 2021 since I would not be able to pay the new tariff. The response I received on 24 May 2021 was that the contract will be cancelled on 30 June 2021, nothing mentioned about my query of increased tariffs and not being enough notice to decide whether I cancel or not. I phoned the call centre and complained about it, on 25 May 2021 I receive another email stating the same, the contract will be cancelled on 30 June 2021 and that the matter has been closed.

Cell C can you please address the tariff increase notice period given to customers and finding a resolution to this.