MTN de***** R5200.00 from 87 year old widow

Unauthorised sim card swap leading to **** of R5200.00 "spent" on my MTN account. Numerous attempts to contact them have been unsuccessful, beyond an email saying that i must contact them in 2 weeks when they can change the spend limit. I DONT WANT TO CHANGE MY SPEND LIMIT I NEVER HAD A SPEND LIMIT I WANT THEM TO REVERSE THE DEBIT OF R5200 THAT THEYRE CLAIMIMG I SPENT. This isnt the first time I have been de*****ed by them and in fact the ***** line itself goes against their own *****ulent practice by asking for OTP - something MTN expressly say NOT to do ("MTN will never ask you for your OTP"). I am an 87 year old widow with no way of paying the amount they claim Ive spent. Please can you help?