After 9 years of loyalty

I have been with MTN ever since I was able to afford a cellphone contract. I have had my account debit my banking account from the very beginning and have never missed a payment. I recently went on vacation to the USA and have been paying money into my account via paypal. Unfortunately, my payment in February didn't process in time and so, my account was debited on the first and the transaction didn't go through. It did however go through the following day and my MTN account is still up to date with its payment and I am not in arrears on any payments. I returned to SA on Friday this past week and went into the Brooklyn branch of MTN to get a new iPhone so I could contact my friend and family. However, after waiting to see if my application had been successful or not, I received an SMS notification telling me I had been denied. I am very angry with MTN that they would deny me from getting a new contract because I had one late payment, not a no payment, but a late payment. I earn a good salary and I have virtually no expenses apart from my cell phone bill that is with MTN and yet I still get denied. Sad to think this is the treatment loyal customers receive