Blacklisted cellphone

I bought a cell phone on Takealot in Nov 2024 and I have been using the phone all along and, all of a sudden my phone stopped working in Mar 2026 and I called my service provider to check if there is anything wrong with my sim card and I was advised that my phone is blacklisted and was referred to MTN and this is the response I received from Mtn Please return the device to the point of sale where it was originally purchased and send us your proof of purchase, invoice and receipt. This is not acceptable at all I bought this phone cash.