Private Onstar Calls

[Joker]

Can anyone help me figure out a way to privatize phone calls I receive/make using my Verizon minutes over my Onstar? It works great via speakerphone, however, there are times when I am not alone in the vehicle and would still like to utilize this service. Help!

[ZZebes]

the older cadilacs with onstar had a mobile phone handset in them but i don't think there is one available