I'm having some problems with iTunes can you help?

I bought an iTunes gift-card at Target last weekend. When I got home I typed in the code and it said that it was invalid. I typed it over and over and it kept saying it wasn't valid. I typed in all the codes on the card at least three times to be sure I was typing in the right code, and I even got other people to try typing it. I tried with Caps on and off but still the same results. I'm 100% possitive that I had the whole thing scratched out too. How can I get it to work? If there's no way to get it to work do you think that I'll be able to return it after I already scratched it out?