Lack of Service from FNB

I opened a FNB account and with the account you get a monthly allocation of air time and data for free. I put the sim in my phone and got the allocated airtime and data. I then ported my personal number to the FNB sim. As with all networks I lost the airtime and data which was not a problem. However, since then, I have not received the monthly allocation due to me. I have phoned at least 4 times over 4 weeks and still nothing has been resolved. How difficult can this be? If you are offering this, surely you must be able to deliver! Really not impressed with the service received or should I say not received.