AT&T cellular service

Have used AT&T cell service in CH to call home in the US at least the last 10 years. Have not had any connection problems or spotty service including at St. Bernard Pass (high in the Alps).

Thank you very much!

That's a lot of minutes. You should do the math to see if a local SIM card would be more cost-effective, even with a burner phone.

When you travel outside of the US with an AT&T phone, you are no longer using AT&T's network, but a local network. Your phone will usually choose the strongest local signal, and in most of Europe, the GSM coverage is much better than in the US.

If you really want to look at coverage maps, here's Swisscom's: http://scmplc.begasoft.ch/plcapp/pages/gis/netzabdeckung.jsf?netztyp=lte&lang=en (remember to choose "2G" for voice, as opposed to 3G or 4G fpr data - you'll see how extensive it is).

Here's Sunrise's coverage map: http://www.sensorly.com/map/2G-3G/CH/Switzerland/Sunrise/gsm_22802#|coverage

And here's Orange: http://www.sensorly.com/map/2G-3G/CH/Switzerland/Orange/gsm_22803#|coverage

I've never had any problems getting good network connections anywhere in Switzerland (or indeed anywhere in Europe). There are a LOT of towers, and one benefit of roaming with AT&T is that your phone will connect to the strongest signal with any network (as Harold mentioned). If you use a local SIM, you'll be limited to using ONLY the towers for that network, and there may be areas where one cell firm has "spotty" coverage.

Thanks for your help everyone

Thanks, all. Don't forget about Skype and other internet-based options, too. Most hotels will have Wi-Fi.