Amazing. Is there no Toshiba forum?
Here is how to forward the phone: (from a toshiba user guide)
#602 = Busy Call Forward-Busy—forwards calls immediately when your telephone is busy or in Do Not Disturb mode.
#603 = No Answer Call Forward-No Answer—forwards calls to another station if you do not answer within a certain time (that you designate). Not available from a rotary telephone.
#604 = Busy/No Answer Call Forward-Busy/No Answer—forwards calls immediately to another station whenever you are busy on another call. Calls will also forward if you do not answer within a certain time (that you designate). Not available from a rotary telephone.
If setting CF-No Answer or CF-Busy/No Answer, press *,
enter the time in seconds, then press #. You can enter the amount of time that your telephone rings before it forwards (08~60 seconds). Always enter two digits. If you do not wish to change the ring time, press * then # to make the ring time the same as the last setting.
You hear a confirmation tone after pressing * and again
after pressing#.
This more to this i.e. programming the follow on digits to voicemail etc. Try this first.