PHONE ACTIVATION

Good day guys I can't activate my iPhone is displayed this information (THE SIM CARD THAT YOU CURRENTLY INSTALLED IS THIS IPHONE IS FROMA CARRIER THAT IS NOT SUPPORTED UNDER THE ACTIVATION POLICY THAT IS CURRENTLY ASSIGNED BY THE ACTIVATION SERVER. THIS IS NOT A HARDWARE ISSUE WITH THE PHONE. PLEASE INSERT ANOTHER SIM CARD FROM A SUPPORTED CARRIER OR REQUEST THAT THIS PHONE BE UNLOCK BY YOUR CARRIER.) What should I do about this? Thanks