MTN Exceptionally poor service!

I was due for an upgrade but initially just wanted a sim, the telephonist was quite convincing and I took the device upgrade as recommended by her the Samsung GalaxyA21s I didn't initially open the box. the invoice date is 05/11/2020. When I decided to use the phone, I put it on charge as required, however the charges runs 100% flat when removing the charger, thus only being able to use the phone when plugged in. I took it to the MTN Service Centre at Centurion Mall. Gladys *** took the phone and was going to return to the ware house for replacement. this was on19/1/2021.She gave me 2 ref nrs airms398380 and***. The invoicenumber ***. then there is a long number ***.It's now become a them and us between the store the warehouse and call centre they are no longer taking my husbands call and have blocked his number. Its imperative that I received my phone from MTN, the service provider. the phone is used for work purposes and use the phones to enter and leave our complex. at this point we swop sims between one divice. I too am paying for a divice I dont have. its most unacceptable. please intervene. regards Celeste