You can easily block calls and text messages to international numbers in various ways:
In the My BASE app: on the main screen, click "More" > "Out-of-plan limits and blockings". Select the type of SMSes, calls or services you want to block.
On My BASE: go to "Limit your mobile usage" > "Barrings". Select the type of SMSes, calls or services you want to block.
Unblocking is done exactly the same way.