Voice calls like a mobile phone

Client enquiry for a proof of concept gateway that when the engineer on site needs to talk to someone, they can make calls like a normal mobile phone. They want to do this as they anticipate having a decent antenna which will get a signal.

I can handle the speed dial buttons, it’s just knowing if it can handle a speaker & microphone for, preferably, hands free calls.

Additionally, related to the other question in the RAK7244C, are there any known issues with sharing the cellular data connection so the Pi acts as a local router to give some other devices internet access?