It seems that the phone is network locked. This means that you can use SIM cards belonging to the network the phone is locked on. It isn't possible to use another SIM card from a different carrier because you will need the unlock code for that network or simply a general network unlock code. These codes can be obtained from a phone service shop or from the carrier where the phone is locked to. Usually these codes are not free and for an unlocking service you will need to pay an extra fee.