You can't just roam on other towers, without them both using the same band (CDMA, TDMA, GSM, ect). When you talk about them not having their own towers, they still have their own equipment, just not the other physical tower, they hang their antennas on others towers. Supposedly Verizon has an agreement to provide service for emergency services and that is why it works there? Markha you should be able to talk on the phone and have data, unless you are in 3G mode, but if you are on 4G, then you should be able to do both.