Subaccounts are not able to purchase their own balance but either:

• Share the balance available on the main account.
• Manage their own balance which is assigned from the main account as a budget.

When you add a Subaccount (Workspace → Subaccounts → Add Subaccount), you’ll be asked to choose between those two options.

When choosing the second option, the moment the assigned budget runs out, the Subaccount won’t have any more balance to continue sending messages. Keep in mind that in this case, a manual action is needed to ensure sufficient balance is available for each Subaccount to keep sending messages.

If you want to ensure that Subaccounts never run out of balance, we recommend sharing balance with the main account and setting up Auto Top-Up here. Here's more information: How to set up Auto Top-Up

For detailed information on Subaccounts, take a look at this article here: Accounts, Workspaces, Users, & Subaccounts.