Unable to cancel expired contact during lock down

I have tried calling Cell C since the start of lock down with no luck. This is simply to cancel my contracts that are due for upgrade which I am unable to afford due to lack of income caused by lock down. I do understand that they are adhering to government rules by closing their call centers but I have made the same calls to every other company on my debit order list and got through no problem as they have agents working from home. Cell C is the only one out of nine companies I called whom I am finding impossible to contact. To make matters worse I sent an email to them stating what I need to be done. They reply twice stating they could not reach me as a telephonic call is needed for security reasons. This is a huge lie, I never received any call from they nor did I miss any calls that day in particular. I have tried using their self service option, the Cell C app and their website to at the very least cancel my recurring bundles with them. There is absolutely no option to do this on any platform mentioned but should you wish to buy a product they make that very easy indeed. Is this even legal? The only way to cancel a contact or even a recurring bundle has to be done telephonically and during these tough times they make it impossible to do so!