Either file as a feature request (to do it from the N900 GUI) or do it directly from your phone MMI. The SS you are looking for is Call forwarding on no reply "CFNRy" (61). Type **61*Number_to_forward_to**45# as phone number and press dial. If you get an error bring the 45 down to 30, since the allow max time is network dependent. Since *# is not working you need to put the SIM into another phone, run the above and change back to the N900..... hope it'll work out.