I called to inquire about returning a purchase and was told that it wouldn't be a probl...

I called to inquire about returning a purchase and was told that it wouldn't be a problem. When I arrived at the store the cashiers were rude to me and told me my receipt was tampered with whatever that means, then the cashier that answered the phone came and helped and said the receipt wasn't tampered with and they were rude to her and still wouldn't return my item. This is upsetting to me because I live Petco it is my favorite pet store and I dont appreciate being treated rudely and was trying to return my item so I could make a different purchase. I would appreciate some kind of resolution to this issue. The store was **** west tropical parkway las vegas nv. The helpful employee was alex. And the rude employees were andrea and Anthony also were being racist towards me and very rude to their fellow employee.