cancel a purchase
how can I cancel a purchase and get refund for an App I just purchased for my iPad ?
You can't cancel a purchase. Once you purchase an app or song, anything at all, the transaction is virtually instantaneous and there is no way to cancel it. According the iTunes terms of sale that we all had to agree to, in order to purchase content from the store - there are no refunds and all sales are final.
However, that doesn't mean that you cannot try. You will have to contact iTunes Store Support and plead your case with them.