When you travel to another country, you would need to take into account the fact that using your smartphone could imply an extra cost for you.
The extra cost will be caused by what is called roaming. Data roaming occurs whenever your phone disconnects from your carrier's network and hops on another network. Roaming allows you to make calls, send texts, and use wireless data even when you're outside of your network's boundaries. The downside, of course, is that roaming data usually comes with extra charges to your account.
The first thing that you need to do is check with your carrier if data usage in other countries is covered in your current fees.
If it is not covered we recommend you to disable data roaming in your smartphone, you can find how is done in the following links:
In case you will need data roaming in the country that you are going to, you can look at companies like Holafly that sell e-sim or physical sims for international roaming.