Find My iPhone issues
What they would do in the store is work with you to make sure you don't really have access to the Apple ID. They would also seek to identify you as the original purchaser - if you can provide proof of identity and proof of purchase, they might have a procedure to erase the lock.

I would work with AppleCare on the phone or internet to see if they can help with the Apple ID. Then you can decide to drive in person to Apple or perhaps see if there is a closer Apple Technician that could assist you with an unlock. The benefit of Apple is they don't charge money for this service - and you might pay someone else to assist.