If you have an iPhone or iPad, you can use your new eSIM data plan for FaceTime as well as iMessage, since they both run over the internet and don't need to be connected to a phone number.
Here's how to make sure FaceTime is set up to work correctly with your new eSIM:
1. Go to "Settings" and choose "FaceTime"
2. Make sure FaceTime is toggled on
3. Your Apple ID (email address) should be checked off under "You can be reached by FaceTime at ..."
This is important because while your phone number might be turned off (depending on if you choose to keep your Primary SIM on while you use your eSIM), your email address (Apple ID) will always work with a Wi-Fi or data connection.