As FoxFifth has pointed out, cellular providers typically do not allow for tethering unless you specifically "sign up" for this service that comes with an additional cost. Regardless, you would need to contact them to have it enabled. Until you do so, you will continue see this message when you attempt to use your iPhone as a hotspot.
Question: I am having BSNL as my service provider.How can I create mobile hotspot from my iphone if everytime I try to do it,it shows contact carrier??