Mtn bad service on repairs

I bought a mtn phone Honor X6A through Edgar's.... Never took off the screen protector or back cover phone had not one scratch or mark on the phone ... Phones battery just went flat and never switched on again.... Took the phone back toe mtn on the 3th September 2024 it was successfully booked in received a SMS from mtn with reference number on the 10th I received a SMS again telling me my phone has been repaired and and despatched back to store I must wait 3-4 working days and collect my phone from Edgar's Greenacres again ... Good I phoned the cellphone consultant to enquire if my phone reached the store she phoned mtn cause than it was more than the 4 days already they asked her to phone back after 3 cause they couldn't trace my phone they not sure where it is ...

She done a follow up the next day again they said my phone is still with mtn and my warrantee has been voided cause apparently I opened the phone.. keep in mind there was no damages on the phone or a scratch on the phone I've send to Mtn.... The price of the phone is R2999.99 they gave me a repair question of R4322 ... I said I am not paying that cause I haven't open my phone and why do they have different stories on my device... I received my phone today 03 October 2024 full of scratches and back cover that's damaged ... Unfixed... Can you please advise me what to do