Buying a phone with contract and cancelling won't work. Your phone would be 'vendor locked' or even 'SIM card locked', meaning it would not accept another SIM card without a long password-like number you won't get when buying this way.

On the other hand, all this is rather easily hackable, and there is thriving market in hacked bought-with-contract phones (well, and stolen ones, too)...

I'll try to find the local price of your Siemens.

Dragi "Bonzi" Raos
Zagreb, Croatia
Q#5196, MkII#80000376, 18GB green