Iphone sim won't work in newly bought iphone?

I broke my old iPhone 4S so bought a used iphone 4 on ebay. The phone is said to be unlocked but when I out my old sim in the phone, it says that there's "no service" and it also says during the set-up "SIM not valid". How do I fix it and make it work?

Looks like someone as lied to you my friend. You are probably gonna have to get the phone unlocked but just a question have you tried any other sim cards in the phone? Just to eliminate that it is your sim thats the problem and not the actual phone itself.

Hi if the iphone 4 displays "sim not valid " message then sure your iphone 4 is yet locked with some other network provider. To fix this you have to unlock your iphone 4 first to use it with your sim card. You can easily unlock your iphone 4 with the help of sites like http://www.theunlockspot.com/apple-iphone-4/rs1wp9/ here they will unlock your iphone 4 using remote unlocking service for affordable cost. After unlocking it you can freely use it with your old sim card…