Why does my micro sim doesn't work in my iphone 5?

I got an iphone 5 and i inserted a micro sim and after some time it says that NO SIM FOUND
What should i do?

I overheard some other people discussing this issue at a trade shop in the town I live in. Apparently iPhone sim cards are just a hair different than normal SIM cards so regular ones (out of Androids, Windows Phones or just old phones) seem not to work on the iPhone 5. I do not like Apple devices so I could be wrong on this just going by what I have seen and heard. I would say call your provider and request an iPhone compatible SIM.