You can directly connect to an Apple Customer Support agent through Apple Support application. Install the application in any of your iDevice using the link below:
Contact Apple Customer Support : Official Apple Support
There are also one-way feedback mechanisms:
If you have a suggestion and don’t want a reply, use feedback form: Apple – Feedback
If you have found a demonstrable bug, report it with Apple Bug Reporter
If you have discovered a serious security, safety, or law enforcement related issue, look at the instructions at Product Security.
You can also send an email to tcook@apple.com. He gets thousands of emails each day, so you probably won’t get a direct response from him either, but someone on his staff will read the email.
If the complaint is relates to a local store, you can go in and ask to speak to the store manager.