Based on the OP's lack of mechanical/bike experience, since he has already given the store a chance to correct the problem and even a bike shop a chance to diagnose and correct with no satisfaction from either, it's time to return it to the store and purchase from a legit bike shop that will stand behind their product and are concerned about having a happy customer, because I get the feeling that the OP will be a regular bike shop customer and there is nothing wrong with that. Not everyone gets joy out of tinkering on their toys, Good luck,