I live and work overseas but have kept my Cell C contact number on WiFi calling so that I can maintain communications with institutions in South Africa

I live and work overseas but have kept my Cell C contact number on WiFi calling so that I can maintain communications with institutions in South Africa. Cell C have discontinued my line despite having maintained a positive airtime balance and now cannot make WiFi calls. I would like someone from Cell C to contact me on my USA number to resolve this issue.