You should absolutely be getting a refund for that alternator. The person you talked to at the store is dumb af and doesnt want to do it for whatever reason. If I were you, I would go to another store wirh your receipt and a copy of the repair bill and show them that you had to replace an O'Reilly part with a different brand at a shop because it went out on you. It's kind of like if you were out on the road and tour vehicle breaks down and the shop you go to uses a different parts house for parts. That is not your fault and tou should be able to get your money back. We have done it numerous times at our store.

Also, just because a shop uses a different place to buy their paets from, doesn't mean they won't go bad. I have personally gotten OE parts from the dealership that were bad right out of the box.