Your International Roaming is a prepaid service. To give you complete control over your spend, you can buy International Roaming credit for your entire trip. To ensure you do not exceed the budget, you set a data usage limit that automatically pauses your service when you cross the data usage limit.
At any point during the travel, you can increase the data usage limit if you wish to use more data than you initially set. However, there is a chance that we may receive usage reports of your Voice, SMS, and data a little later than expected. And when that happens, your International Roaming charges may reflect across multiple bills.