Can I migrate between plans?

You have some migration options between plans in ElephantSQL.
Fork: Easiest is to fork your database to a new server. This can also be done for plans with followers.
Backup and restore: Another option is to set up a new instance, take a backup of the old one and import your data into the new instance.
Pipe data: You also pipe your data to a new database: pg_dump postgres://user:pass@host/db | psql postgres://user:pass@host2/newdb

More information can be found here: