I had a friend that was also called a liar by a manager at one of their stores. A salesperson told her one thing about an item she purchased, and it turned out not to be true... when the item stopped working, she complained to the manager about what the salesperson told her, and he told her that it didn't happen, "they don't give out advice like that". She eventually got the matter resolved, but it shouldn't have happened in the first place.
Oh, and the Geek Squad? Most of them couldn't fix a computer well enough to compute their way out of a wet paper bag.