Activation my redeem iTunes gift card Please

What you normally should do is go back the retailer from whom you purchased the card and discuss the problem with them. They should either correctly activate the card or give you a new one. If they refuse to help, as some retailers do, go here:

iTunes Support

and follow the instructions to report the issue to the iTunes Store. They will ask for a scan of the front and back sides of the card as well as a copy of the receipt

Regards.