Airtime disappearing within seconds

I loaded R30.00 on 22/10/2015 and just as I was about to make a call my airtime disappeared. i called the call centre to query and was told with an attitude to Dial *141*5# ( which confirmed on numerous occasions) that I am not subscribed to anything. I was also told that it has nothing to do with mtn and that I am subscribed to something and was referred to another company other than mtn on ***. I loaded R30.00 again on 25/10/2015 and the same thing happened without any calls, I then loaded 10mb of data and that disappeared too. I called this morning and was referred to *** and then referred back to the call centre and still have not received any assistance. None of the consultants and even the team leader are qualified to handle queries or assist and advise the nature of my airtime being taken. they are *********** and do not know how to assist customers with queries!!!