How can i get an upgrade? ?

I got my blackberry 9300 in october with a 24 month contract of 25.00 a month..I use international calls so my bill is usually �70.00 a month. I didn't realise that the new blackberry looks similar to this but is around 300.00 was out a few weeks after. How can I get an upgrade? Its with 02 but carphone warehouse store