Poor service

For the past 3 months I have been loading airtime in which after a month the airtime gets finished.this is a new SIM card which I have not subscribed to anything.i have called the customer care on many occasions in which I have been advised that they cannot seem to identify the fault and after a few more calls I have been advised that the number I am using is subscribed to certain things from previous user of this number.this is not my problem as I have not subscribed to anything and the problem has not been resolved.this is terrible service.