MTN *****

I have a contract with MTN for more than 20 years, on the 9th of March 2022, someone bought 2 iphones 750 online on my contract, change my address to an invalid address. I reported it to MTN and as I am in Botswana, I went to the police and reported it. Send the police declaration, my ID and the statement to MTN ***** department as well as to complaints and Mondo. I could not call them, the numbers they gave me is not reachable from Botswana. I then also gave a friend permission to call them on my behalf. He also did everything they told us to do. I changed my account to a cash account and paid my contract. The only respond that I got was from Mondo, that the transaction was invalid and from complaints that my account is overdue now. What else can I do? I have copies of all the correspondence with them.