Proof of Purchase

I am a former Nashua Mobile customer who was migrated to MTN. I broke my phone screen on Wednesday and Samsung requires a proof of purchase to repair it. I went to an MTN store and they said they cannot give me a proof of purchase as the contract was taken out with Nashua Mobile. Nashua Mobile no longer exists. All their numbers do not go through. The consultant was rude enough to suggest that I should have not lost my original contract because they did not migrate this information. How is that proper customer service? In the meantime I do not have a properly working phone. I even called the call centre and they gave me another number which did not go through as well.