SIM NOT SUPPORTED
SIR;
message appear that "SIM NOT SUPPORTED"
iPhone 6s Plus, iOS 10.3.2
This kind of error, can indicate two things:
Your Sim card is defective
or, (almost always)
Your iphone is carrier locked. Please note that if it is locked by a carrier, nobody here can help you. Only that carrier can unlock that device (if you qualify).
Read this support guide:
How to unlock your iPhone for use with a different carrier - Apple Support
Regards
Giulio