What??????Service??????

I'm very gatvol for MTN. I upgraded in January to a Samsung A34. In February I got my new invoice and they started charging me on a new number for a Samsung A12. I've been calling since February to get this removed from my invoice because it is not my contract but still, they invoice me for the Samsung A12. I called the MTN store that did the upgrade and complained and they also logged the issue with MTN but still, I am invoiced for a Samsung A12. On 18 June 2024, I sent an email to MTN regarding this matter because phoning them doesn't work and still this is not resolved. They don't even respond to the email. Today I phoned again to follow up on why I haven't received any feedback on this matter and why this is not resolved yet, and all the lady can say to me after checking everything, "The system is offline" but she could check all my details and reference numbers.