I would at least try to dispute the charge with your credit card company. They will probably allow you to begin the process of disputing the charge which will force Mr. Bad English to reply and explain if he wants to get paid. Most credit card companies have pretty liberal dispute policies. If he fails to respond in the required time--he doesn't get paid. If he responds, at least that will possibly give you time to take it somewhere else to have it looked at and find out what the problem is. You're probably going to have to resort to going somewhere else to get it fixed--the shop you have been dealing with sounds completely incompetent. They obviously are not going to fix your problem. I don't know much about stereo systems but this sounds like a relatively common problem and any competent business should be able to fix it. I remember hearing friends' systems back in high school that had this problem and they put the system in themselves, I've not heard of anyone having this problem after a supposed expert installed the system. I wouldn't trust Mr. Bad English to give you the straight story. It sure is easy to blame a part he didn't sell you rather than his incompetence. My suggestion is call Mastercard today. Then you'll probably have to get it fixed at a different shop--ask around for referrals. Another idea, call a few shops in your area and ask how much they think it might cost to fix after explaining the problem. And for God's sake--stay away from Mr. Bad English, don't let him touch your X again. It will only cost you more money and headaches.

Good luck.