Dude seriously, post a complaint with the better business beraue. Businesse's are very eager to keep their status with the BBB on a neutral level. If they don't have an account with the BBB then the BBB will open one with a negative feedback. If you need more advice let me know (pre-law major).
Also, I had a problem like that, and the manager refunded me money and bought me new spark plugs. Be aware that it will take time, but they will answer!
Good luck, dont put up with B.S. Bro