I use my iPad Pro (they are all unlocked) and buy a local SIM for it. Then I just use the iPad as a hotspot for all of my devices. If you are using iPhones then you can use FaceTime Audio for calls (or Skype, etc). Also, if you have Wifi Calling enabled, in many countries your iPhone will show as (in my example) AT&T Wifi and you can call any number as if you were back at home.
Hope that helps!