Hello SallyMark, sorry to learn about your experience. The best way to avoid unwanted international charges is to turn on Airplane Mode on your phone when leaving the country.
i had the same experience as you and many others in this community. The Travel Pass is flawed and does not work as advertised. I turned off Cellular data and roaming and even turned off individual apps from using cellular data and still got messages that I had activated the Travel Pass for a day. The day i actually wanted to use it and needed it, it did not connect to a network. My solution is to remove the Travel Pass from your phone account then either leave the phone at home or get a SIM card in your destination country. This service apparently is generating good revenue so Verizon seems to have little incentive to make it work.