This is called "forking".
You don't fork calls that come into the phone port, you fork calls that come in on each individual service, SP1, SP2, Line, Obitalk etc.
Go to the service you want to fork calls from and add your cell phone to the inbound call route.
Example:
Voice Service -> SP1 Service -> X_InboundCallRoute = {ph,(18005551212)}
it may just be ph now. with more than one rule you need the brackets {}