Poor Service

I am trying to do an upgrade. When I contacted the call centre I was informed that I cannot get the handset I want because I have a "Low credit score" the reason given is that I pay via EFT instead of a debit order. I am staying on my current contract with no changes. I asked the call centre agent to escalate this matter which she did. I received a text message with a ref no. About 10 minutes later I received a text message informing me that the case is closed with nobody contacting me at all