HELP!!!

I bought a coat around $100 in Winners on Dec.26,2008, then I went back to return it on Dec.27. But the casher said the price tag is not for the coat. And the store manager said the same thing to me and they refused to return it for me. I don't know why and how the tag is not right. I explained to the store manager and asked why nobody said anything when I bought it and charged me the price on the tag. The store manager said I was screaming to her and called the security. Then I came back home and called Winners customer service. A woman replied my call and say they need to ask the store manager about it. I have been very patient to wait for them to give me fair answer but it's so surprised that I got a letter from Winners today saying that I'm not allowed to enter any Winners store from now on, otherwise I'll be arrested. I'm so angry about this, it really hurts my feeling. But I really don't what I can do next. Could someone help me on this? Thanks a lot!

By the way, I'm in Canada. I've never been through this, 气死我了！