I would take it back to the shop and ask them to fix it. I agree that it sounds like something got moved that shouldn't have.
There are many feet available to do different things. Although this is a Bernina site, Singer has many of the same feet, and I have bought mostly generic ones for mine.
http://www.berninausa.com/content-n401-sUS.html
I hate when sales people don't take the time to show and explain what they are talking about... not everyone is a seasoned sewer :roll:
Many people don't know what a certain foot is called or a particular stitch either...but that doesn't mean that we don't know how to use them :wink: