CELL C - PROBLEMS

Hi my name is Lorraine I have been having issues with a cell phone I took on contract with Cell c for about 2 months now & my contact is only going into its 6th month. end of Jan 2021 I took my cell phone to a chatsworth store & it was sent for repairs. I received it about a week and half later,it worked for a few days & then the same problem experienced. I went back to the store & the consultant that assisted me that day couldn't book my cell for repairs as she told me ,she couldn't see the serial number & I should return with the original box, This left me confused as on the first time it was booked for repairs the phone was the same with no serial number at the back ,further to this the consultant told me that on that particular range of cell phones which I had taken were very problematic (DEFECTS). I sent an email NO reply from them.called the call centre and the collected the device .I do a follow-up today and they say that the couries have not delivered to there repairs centre yet.DEvice collected on the 24.02.21. so please I need some help as even though I don't have the device I'm paying my instalment and all I ask is I get feedback or replacement device.SO disappointed ,a customer for over 10 years.