Roaming charges inside of the EU were eliminated in 2017, so a single prepaid SIM (readily available for a few dollars) would do him well inside of the EU. Mak

Roaming charges inside of the EU were eliminated in 2017, so a single prepaid SIM (readily available for a few dollars) would do him well inside of the EU. Make sure that he has a phone that's not vendor locked. That doesn't include Switzerland, and may not include the UK by the summer, but the SIM will still work there, just with additional charges (which are usually fairly reasonable).