Cell C refuses notice to cancel Contract

I sent two emails to Cell C one via the app the other on their website to give notice to cancel my contract which ends January 2022, I got sms saying I should call to finalise the process when I called the number I got a response that said I've reached them after hours. I tried calling Saturday, Sunday and even Monday I get same response from their robot. It's clear to me that this is their way of making sure that the contract never ends, it's their way to keep taking my money by force