How to hang up the cellphone call first

 

I wonder how you can hang up the cellphone call first on your Bluetooth enabled TomTom GO 930 unit? Because I don't know how, I hope the caller/receiving person at the other end hangs up and my GO 930 unit would return to normal. Currently, when a cellphone call comes through, I am asked whether I want to answer or not. If I press the Yes button, I get to talk with the other person and my GO 930 screen goes back to the Map Mode with no button available to press when I am finished with the call. Is the Cancel Call button on another screen?