How to check my telephone model by IMEI?

No. Not to check by IMEI. I can only assume that you bought a gray market phone.

Apple DOES have a service where you can check the serial number and it will tell you if it's in warranty and when the warranty ends.

You can check that here: https://selfsolve.apple.com/agreementWarrantyDynamic.do

You might like to try this site also, type in your serial number and it will tell you the year of production and at which factory in China http://www.chipmunk.nl/klantenservice/applemodel.html

Why don't you just look at the phone?