Yes, you can.
To change the account associated with your subscription, you’ll need to delete the current account.
Bear in mind that all data will be permanently deleted from your current associated account.
If you don’t want this to happen, you’ll need to upgrade to an Agency plan.
To delete your current account, follow these steps:
User Menu (top right of the screen) > Manage Accounts > Delete
After that, you’ll be able to add a new Twitter account and start gaining real followers!