Is there a way to dial multiple digits during a call without transferring the call over to the phone and entering the digits on the phone?

I just set up my bluetooth connection and my maiden call was to my bank. The first question they had for me was to enter my account number. I didn't know what to do.

 

You don't need to transfer the call, but you have to enter the account number on the phone keypad, AFAIK.

I generally pull over or stop to initiate such calls, although I do risk accessing my voicemails by dialing the access codes while moving.
For security reasons, I do not store such numbers on the phone for dialing/sending.

 

The 'SEND' verbal command works for me when accessing my voicemail.