Apple Authorized Service Centres

Hello,

How may one reach Apple's central or top-level office for service centres? Any phone number, email-address, URL?

I have had an appalling experience with an authorized service centre's technician. He talked nonsense, lacked knowledge, and misled me, and I want to give the lowdown to the right people at Apple because they need to hire more knowledgeable persons and make sure they know what they're doing.

Thanks.