Currently, you can't switch to a different provider or change the email address after you selected one, this is something we are working on but it isn't available yet.
The best alternative, in this case, would be for you to create a new Drops account with a completely different email address on the very same device. The system will then automatically sync both and transfer all your progress and purchase from your old to your new account.
If the sync doesn't work correctly, please get in touch with us through the Help Section of the app providing us with the email address associated with your old and new accounts.