After 15 years i still get treated as nobody

my mum has had a cell c contract for the past 15 years! her cellphone is due for upgrade she has app**** for the S6 edge however cell c cannot provide her with a gold one.they are trying to rub off a black phone on her. the call centre sent a black phone to her which she had returned as we got a gold one in lenasia. upon reaching the branch Aadil who is very arrogant says she does not qualify for a phone that was delivered to her the day before.I need to understand how is it that the call centre can proivde the phone but not the branch if it is one client with one ID number. i then called cell c customer service where all sorts of promises was made by charmaine. to date i have not recieved feedback. instead of buying people out of their existing contracts service your existing customers.