Proof of Purchase

I am unable to get proof of purchase for a cellphone for the past 3 days. No one gets back to you. Because I got the phone online they need to get the Proof of Purchase from a third party evens thou MTN advertised the promotion and my Contract is with MTN. A customer for over 10 years... SO now I have a broken screen and i can't claim against my policy to have it repaired as MTN cannot provide me with a Proof of Purchase...