In order for them to fix it without asking, you have to sign some paper before hand saying that you want them to look for the problem, and that you agree to pay for parts and labor for the repairs. Look for the part about them fixing stuff, cross it out, and have the service rep and youself initial it. That way when they fix it anyway and try to charge you you can sick your lawyer on them .

Personally, I couldn't say what your problem is.