While you can have as many as 14 sub accounts under a particular campaign, all accounts will be billed as one entity. If you need separate billing, then multiple campaigns with distinct login credentials will need to be created. Note the following with creating multiple campaigns:
A distinct email address for login will be required for each account you create.
You will not be able to view the data for multiple campaigns under the same username, i.e. you must log in separately to view each campaign.
Each new campaign will be billed separately.
For more information on sub accounts, feel free to visit this article. Should you have any questions or concerns, please do not hesitate to contact our Customer Service team.