Samsung Galaxy Y Young Disconnection Problem! Please HELP!

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http://androidforums.com – Hi there I brought this samsung galaxy y phone on a buy and sell site and everything was going ok until I decided to restore factory settings. When I'm trying to send sms or call someone it is coming up with an error message saying mobile network not available. So I went into settings-about phone-status it says that the service state: is out of service and the mobile network state: disconnected. Can anyone tell me what I did please? does this mean the phone is locked or something? thankyou (General)