Cell C permanently blocks SIM card used only for data

My internet service (LTE) was provided through a Cell C SIM card inserted into the router by Cell C staff at the Cell C Olympus Village store less than 12 months ago. Since Saturday 28 March 2020, two days into lockdown, I had no internet. It was noticed that there were other people who also could not connect to Cell C. On Monday when I called Cell C Customer Service at 11:20 am I was merely told that my SIM card had been permanently blocked because I did not use it for airtime/talking and I must buy a new SIM card. This SIM card number is now being recycled and will be given to someone else. There still must have been at least 10-17 GB credit on the card. It is lockdown, I am older than 70 with elderly people constantly warned not to go out. Nobody ever made me aware that I should use the SIM card for talking and they definitely must have noticed that I only had data on the card each time I called to check my balance. How does Cell C explain this disgusting conduct, including how one is supposed to use a router for talking?