Unacceptable service from the manager

I bought a Samsung A32 from Cash Crusaders "Florida Lake" branch. 3 weeks later the phone was blocked from using MTN network. I head over to the store to see what they can do for me as a customer. The Manager made it seem like it was my fault because I didn't come within 7 day period. I was willing the pay the difference for another phone but the manager insisted it needs to go for repairs. The phone is blocked! Please teach your managers customer and people skills please. I have been buying from that store for as long as I can remember.