How do you know the iPhone is not locked to a particular wireless provider?
With which wireless provider in what country are you attempting to use the iPhone?
From what seller in what country did your father acquire the iPhone?
Do the following In the order given until the problem is resolved:
Remove the sim, clean the contacts, replace the sim.
Obtain new sim from wireless provider or borrow one from friend/relative/co-worker
Make an appointment at the nearest Apple store to have your iPhone evaluated.
Once the diagnostics are complete, the staff will explain your options.
Make a Genius Bar Reservation
http://www.apple.com/retail/geniusbar/