About SIM CARD

I just put Sim card in iphone 7, have last update 15.7, they told me:

SIM not supported

The SIM that you currently have inserted in this iPhone is from a service provider that is not supported under the activation policy that is currently assigned by the activation server. This is not a hardware issue with the iPhone. Please insert another SIM from a supported service provider or request that this iPhone be unlocked by your service provider. Please contact Apple for more information.