greta -

Return to the shop where you purchased the bike. Get a copy of each invoice where they have adjusted your bike - most shops today record everything in the computer. The bike needs to be properly built for it to work correctly. Since this bike has introductory quality components, the components will need regular maintenance.

Also at this point, only deal with the store manager and the head mechanic. Calmly explain your frustration in the quality of the build and the quality of their repair. Give the shop one more chance to get the bike working properly. You have two options then - ask/demand a full refund or go to Giant's website and contact them directly explaining your dealings with this particular shop.

Although I no longer sell Giant, Giant will take all dealer complaints seriously.