kishan, I've checked the phone is a Quad-band as you see from the spec in this page:

http://www.t-mobile.co.uk/shop/pay-m...sung-galaxy-s/

Quad-band essentially means:

GSM&EDGE Band 850 / 900 / 1800 / 1900
3G Band 900 / 1900 / 2100

Here's another page for your reference:

http://www.samsung.com/uk/consumer/m...=specification

As for the unlock, they would do it for £15. Do you wish to go forward?