trying to reset and erase all content on iphone 4s w broken wifi and no carrier

I'm trying to erase all content on my iphone before I sell it. The wifi is broken and I've deactivated the phone. When I try to reset and erase all content, it's asking for my apple id. After entering, I get an error that I need connectivity. I've tried connecting to itunes and reseting phone that way, but itunes complains that Find My Phone must be off and when i try to turn it off, it again asks for my apple id.