TFG CONNECT POOR SERVICE

I've signed a contract with TFG connect for data on July 2021,we agreed that there are going to put data on my existing phone which they're doing till today. My problem is I can't make outgoing calls on my sim card since last year July 2021, I've tried to call for assistance but I'm not getting help,they keep on promising to help and call me to say my case has been resolved but I'm still facing the same problem. What type of service is TFG connect giving to us customer's? The recent lady I spoke she says to me it's because I don't have airtime while I've topped up my number with enough airtime but still it says I can't make calls because it says I don't have enough funds to make calls. What must I do now to get help or I must close my account because I just can't live by receiving calls but not able to return calls.