It was premade, and, presumably sold "as is", in which case, the buyer isn't entitled to a refund. You offered to correct the things (for free!) that they didn't like, and got told no. If you had further contact with this person, I'd say that you're not going to issue a refund for a non-custom piece. Offer again to fix up the things they're complaining about, and if they say no again, tell them sorry, but you aren't issuing a refund for the suit.