So you returned items to the store, price tags attached, and using a receipt associated with those price tags, and it turned out that the items you returned were not the items associated with either the price tags or the receipt? And some of the items were used? Whatever your intentions, you can see, I'm sure, why the store believes you were trying to cheat it.

If you are not able to retain counsel, have you requested an apointed attorney? Given the prior conviction, it would likely be a good idea to do so.