Credit Vetting Nonsense

i called MTN to request that I get a contract with a credit score of 639 and mind you I am only 22 years old , so my application got declined and nobody bothered to even explain as to why it was declined , my question to MTN is , can you guys perhaps not see that one is young , Im fresh from varsity , WHERE will i gets so many debts from , my salary proves that i can afford the device but because in south Africa you need to be in high debt to get anything on contract is what i do not understand , and why does the so credit vetting you use not tell clients where they have faults or where they need to improve????? BAD SERVICE for such a known brand in South Africa , it is disappointing that to be considered you must have a great deal of debt and the BIG QUESTION IS WHY???????