Apple does not keep or stop keeping any accounts when you change providers. It is up to you to update your account info if it changes. Apple has no way to know you changed providers.
Unless you created a new Apple ID with the new email from your new provider, your account remains the same and will continue to use the email address you set it to use.
If you did create a new Apple ID, then you now have 2 Apple ID, and they cannot be merged. You can use Family Sharing to link them so you can access the purchases of one from the other.
To update an existing account with a new email address, see here: link-> Change the email address you use as your Apple ID - Apple Support
To use Family Sharing between 2 or more Apple IDs, see here: link-> Set up Family Sharing - Apple Support