where from this number 080-035-81573?

i recieved a call from this number 080-035-8157 today, they said were calling from three, and that i was able to get an upgrade (free phone) they took some details down,

i think it may be a scam. i just hope they cant do anything with my details.

any advice?

 Feb 05th, 2009
a call from this number disconnects as soon as i answer,i don't recognise the number and i'm sue i'll be charged if i call back or is this what they want me to do.
g jenkins
 Jul 25th, 2008