certified apple repair locations

If you've had a bad experience with an "Apple Authorized Service Provider" you can contact Apple's customer relations department on the phones via an Apple Support call to both provide direct feedback, and to see if there's possibly any way they can help.

https://support.apple.com/en-ca/contact

If this is not an official Apple Retail store then your should use N. American contacts from this page: Contact - How to Contact Us - Apple

We are not Apple employees or agents so can only go with what information Apple publishes. There are no longer any support/reseller feedback links where you can report this so you will probably find phoning them or using snail-mail are the best options.

Right now I am not finding a web page that helps you determine if Apple considers a specific shop an Apple Authorized Service Provider (Apple will not use the word "certifiied"). Perhaps a call to the Apple 800 number will find some one who can look it up for you.

Contact the store's manager.

You might try this https://mobile.twitter.com/AppleSupport