What went wrong with my mobile device application

My application with Telkom for a device contract was just declined due to "credit vetting" what's that?.at the beginning of the call the agent asked me for ID number to check if I quality then he told me I qualify then asked for my salary details to check if I qualify for the device which I want and he told me I qualify then we proceeded with the rest of my application,work details,banking details and next of kin, he even explained the delivery process n everything..Few moments after I get an sms saying I don't quality cos of credit vetting?what's that?.I only have 2 clothing store accounts which I'm paying extremely well, why would I be told I qualify then later receive an sms stating that I don't