Bad service

Sent in my phone for repairs the 23 April 2019. I kept contacting the repair service and they don’t see my phone on their system. I went to MTN each time they told me they will hear where my phone is via their supervisor or someone higher in position. They told me they will get back to me 3 times but they never did. I tried calling them but there was no answer, I sent 3 emails to the repair service and it was always the same answer they don’t see my phone on their system. It is 5 weeks now almost 6 (they told me it will take about 3-4 weeks). This is not on I can’t wait 6 weeks for my own phone and they can’t tell me where my phone is.