Even though your JoAnn's is being sympathetic to you, it ultimately is their responsibility (IMHO) to help you get this resolved. Clark Howard (consumer expert who started on radio in Atlanta) says one good way to get their attention is to go into the store when there are lots of folks in there and ask about your problem, not in an unkind voice, but in one loud enough for folks to hear. They don't want people knowing their customer service is that bad.
Also, does your local TV station have a helpline where the reporters check into your problem?