when I get my winning money chevrolet motor uk on there 2012 anniversary.

Dear sir,  I  receive a taxt on 8 nov 2012 that my mobil number won 500000 pounds from chevrolet motnr UK.there one agent call me and demand me Rs 15000 for registration charge .I sent him his demand money.But he not transfer my winning money.I not understand this matter.please help me and salve my matter.What is true and what is false.my mobil number +919851404561,my email gdolui2000@gmail.com