I would give them the opportunity for a do over,with a different tech.

If they don't do any better, or refuse the offer, take it to another shop. If second shop can produce significantly better results, return to shop 1 with new printout, and request a refund.

If they don't offer refund, blast social media with truthful details about the experience. Don't rant, just state facts and proof. Their results didn't measure up. Gave them a second chance, but no resolution. Went to another shop that had no trouble doing it right the first time.