If you choose a single country plan, you will not be able to use it in other countries.
Please note that in case that we detect any data usage in countries other than the one you applied for, according to Article 12 of our Terms of Service, we may charge you a network fee separately.
If you use multiple countries plan, as long as the country is in our coverage, yes you are free to use it.
For details on supported countries, click here.