I do not wish to accept voice calls, can I disable voice calls?

You can choose to accept or reject voice calls. You can apply this setting individually for different personas and this setting will apply to the voice calls with all friends in that particular persona.

To enable / disable voice calls:
Go to Dashboard > enter a specific Persona > Tap the pencil icon on the top left hand corner > Tap Privacy > Turn ON / Turn OFF β€œAccept Calls”.

You will still be able to receive voice calls after you disable receiving voice calls.