You can add more data to an active plan (data is not depleted and expiry has not passed) in the iOS app by navigating to the My eSIM page -> specific eSIM and click "Add more data". We recommend doing this earlier on, once your eSIM expires or data depletes, you will not be able to add more data to the eSIM.
If you purchase the eSIM on the web and do not have access to the iOS app, we do not currently provide the ability to add more data on the web. We are working on delivering this feature, please let us know if you have any feedback.
Check out our website: getnomad.app