How I can change or reset my SIM cards

Question

I am trying to change my SIM card to boost on my Nextel phone .can i reset the SIM card somehow ,because it is just telling me that the service is restricted and i do not know the pin ,cause i bought it off e-bay and didn't know to get it . is there a way i could set this up on my old phone ? it is a Nextel i870. please help.

Answer 1

 You need to Unlock it To change the Network Sim Card,get the Unlock code at here 

http://www.onlinegsmunlock.com/supported-phones/rs7wp7/ and Unlock it.