As far as i know, the network shouldn't matter. Move all your contacts to the phone memory on your old phone. Copy all (or as many as you can) to your SIM card memory. Put SIM in new phone. Copy Sim memory to phone memory. (If you haven't got all the contacts in one go, put the SIM back in your old phone, delete all the contacts from it and copy the remaining contacts from phone memory to SIM memory and repeat process). Should only take a few minutes.