Per this

http://support.three.co.uk/srvs/cgi-...=obj%286153%29

For PAYG phones, there is a list of access codes making many countries pennies per min instead of £s.

Not available on contract phones?
Is there any Three alternative then, for cheap international calls on a contract phone?

I have a 13 month old Three contract and now want to keep the number but change to Three 321 - what are my chances?

http://www.dialacode.com/

Three also offer 3000 international minutes for £15.32 a month to contract users. I suppose it depends on how many international minutes you use each month.

http://ask3.three.co.uk/SRVS/CGI-BIN...ile:mobileUser