FNB Sim.... what next

Recently I received an FNB sim card which is on my FNB app, This costs R399 per month, I only utilized it recently and found that its always on network not available, I eventually got hold of FNB asked the consultant why is there never signal and I eas told to reboot and take out the sim card and replace it again. Seemed to work here and there. I have tried calling them and also emailing with no response, calls cuts off after a few words, Ivwas told itvis on vodacom and cell c, well I have another vodacom sim and that works fine. There was a balance if 44000 lets call it units and 1.5 gb which I recall The balance on gb was 1. 2... I now received a message to say I need to pay R407 and they have zero'd my call units as well as the data. Really, unfortunately I havent been able to speak to a hunan who could explain what is going on. I look forward to your response. Regards Sharon Mitchell