Use a dedicated Android Auto phone without service to make a call through a secondary device with service

I make deliveries and am constantly in and out of my truck all day with my phone. I don't have wireless Android Auto and all the adapters I have tried are spotty at best. So because Android Auto did not like constant plugging and unplugging, I got a dedicated truck phone. I did originally put a plan on it and anyone I wanted to call or text I would just make sure they knew the second number was me. Well, I found out that OnStar hotspot through my truck is a lot cheaper so I canceled the plan and just run the Android Auto apps off the truck's wifi. The problem I have is now I need a way for the truck phone to make calls on my actual phone, reading and responding to messages would be cool but the work around I found was using FB messenger as my messages app on that phone. A better solution would be appreciated though. I want to be able to stay in Android auto, press the PTT button on the steeringwheel, and tell AA to call my wife and instead of giving me the "please check your phone has service" it just calls on my actual phone. Kind of like how some tablets will let you make phone calls and texts messages through your phone. I want my truck phone to be that tablet. The way I do it now is I turned off "Hey Google" on the truck phone so when I say it only my actual phone responds and I tell it what I want. It works but if there is a better solution to this very specific problem.