Samsung s5230, idiot friend locked my phone when

Did he lock the PIN Lock or the Phone Lock? if its the PIN code then you will have to get in touch with your netwrok provider

Hey,
Call your service provider to ask your Samsung Network Unlock Code. when you change your current network provider you must need to Unlock your Samsung first. after unlocking you can use your Samsung to any network.but network provider take time to give your imei unlock code.
second option is,
you can buy your Samsung Imei Unlock Code from third party . this is safe way to Unlock your Samsung . they will charge little amount but they give your Samsung SGH-S5230 Imei unlock code immediately.
i hope this information is help you.