Voice and Data with Verizon

Can you clarify your concern? If you have a Verizon international plan - the monthly plan or Travel Pass - I don't think there are roaming charges. Your voice and data usage is included in the package, with some limitations of course (there is also a "Pay-As-You-Go" plan - not sure why anyone would want this). If you are asking how to avoid charges while traveling, because you don't have or intend to use an international plan, then keep your phone in airplane mode to avoid cellular usage. Make sure Travel Pass is inactivated if you do not intend to use it, I've heard of instances where it was automatically activated, unbeknownst to the user.

As TheOrdinaryRebecca said can you clarify your concerns? If you have an active international plan, your phone is authorized to use that foreign network, whether that is the pay-as-you-go plan, the monthly plan, or Travel Pass. On those plans you are paying your access fee, such as Travel Pass's $12 a day, but are not roaming. I have the Unlimited Ultimate plan that includes international use. If you want to go without a plan and to avoid roaming charges, place your device on airplane mode and keep it on that until your return home.