SIM card not Supported

My Phone says that the SIM card is not supported after I restarted the phone... the thing is that I've used this sim card on the same phone before it was restaarted. The error is says Is:

"The SIM card inserted in this iPhone does not appear to be supported.

The SIM card that you currently have installed in this iPhone is from a 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 iPhone. Please insert another SIM card from a supported carrier or request that this iPhone be unlocked by your carrier. Please contact Apple for more information."

Ive also tried to use a diffirent sim card from a different carrier. if any one has an idea of what to do let me know, i havent tried contacting my carrier simply because the sim card for them is not supported and idk what carrier its supposed to be from.