Hi there,
Perhaps something can be done with a service like Twillio. Unless there is a python package you have in mind.
If Twillio or a similar service works, perhaps you could embed that service into an Anvil web app. There is an SMS example, so perhaps VoIP is possible. I’m really not sure.
Other may have a better sense of whether of not this is even possible on the Anvil platform, but as far as I know, there are no built in VoIP features. Very intriguing idea though.