I have an international buyer interested in my Sprint 4S. I've disclosed that if ever they come to the U.S., they will "not" be able to use it on any network other than Sprint (and that's only if Sprint has a pay-as-you-go plan allowing this model to be activated). Sprint's pay-as-you-go plans only allow for certain phones sold by them directly. My question is, I had Sprint unlocked the 4S when I purchased it 3 years ago for international use. If I reset it as factory new, will the "international unlock" still activate when the purchaser sets up the phone using an international sim from his/her country?