MTN - no airtime received but being billed

I did not receive my R500 airtime lik usual on the 2nd of July. I logged a query om MTN SP & received no response. I contacted the MNT in Randhart Alberton. I was told MTN can not find me on the system & please send my ID. After sending my ID received an email saying MTN can not find me on their system. I responded to the lady at MTN Randhart to say I receive an invoiice each month & MTN can debit my account! I was told by MTN the money the will be scheduled to be loaded last week. Still nothing. I went to MNT New Redruth and still waiting for a phone call!! MTN can debit my account but does not have a record of me!