Warranty is valid only in country of original purchase. You must
return the iPhone personally or via a friend who can take it to
Apple or AASP in that country and then ship it back to you.
Cost of shipment is yours. Apple will not accept international shipments
for repair and will not ship internationally after repair - especially
to Iran where Apple products are under embargo.
I have bought an IPHONE 4S (In Iran)
The iPhone is not available in Iran. In fact, it is illegal to export it to Iran or to give or sell one to anyone with the intent of taking it to Iran. It can not be serviced in Iran by Apple or any authorize Apple agent.
You will have to determine what country the phone actually came from and take it to that country or send it to someone in that country to have it serviced.
Keep in mind that if you send it to someone, they can not legally send it back to you in Iran.