MTN Customers service

i Went to MTN store at Maponya Mall 2127 Old Potchefstroom to upgrade the contract on 03/11/2018, Sales Person - Garnet Matsoso, assisted me, he did a sim swop on the computer, as I wanted to use my old sim card which fits into the new phone, Since day I got the new phone if I load air time, I get a message from MTN 136 to say I borrowed R50 Airtime,

I contacted MTN call centre to ask why it says I borrowed airtime, then they told me that from 03/11/2018 till 09/11/2018 I am borrowing R 50 = R 250 per night from 21h30.

every time when I load air time it disappear, which means MTN/somebody is using my number and I think it was cloned, because Garnet Matsoso used Cloneit to set up my Phone

I do not get any satisfying help or solutions from MTN Customer service

I want the matter to be resolved ASAP,