Bad Service

Telkom what is wrong with you. I'm on pre paid and have sufficient airtym but each time I try to make a call, I get a message saying my balance is insufficient. Why is that. This is not the first time I'm complaining about this. I wrong you guys an email that was about ywo months ago. I did not get any response from you. Now 2021 I'm bringing this to your attention again. Please assist.