Actually you can. My "published" phone number is parked at a voip firm, and I get calls on that number over data (fairly few real ones, since my friends tend to

Actually you can. My "published" phone number is parked at a voip firm, and I get calls on that number over data (fairly few real ones, since my friends tend to mostly use whatsapp to arrange social stuff.) When I travel, I buy a 25GB-for-a-month physical sim from 3UK, sold on the US Amazon site. The only downside is that you can't top up the data using the same pricing unless you're physically in the UK, so I have to get a new sim each trip.