I doubt the possibility of recovering your deleted contacts.
However, the above procedure will initiate a factory reset, there by effectively bring back the phone to it's original status as when you bought it. It also will delete all data including contacts, SMS, Music, Photos etc. A backup should be done before doing this.
Factory data reset: Reset your settings to the factory
default values and delete all your data.
Press and hold the Power key for 8-10 seconds and release. The device will
reboot automatically.
If this does not solve the problem, perform a factory data reset. In Idle mode, open the application list and select
Settings → Privacy → Factory data reset → Reset phone
→ Erase everything.
(User Guide page 115 & 121)