If you go to Settings > Numbers, you will be able to all your available numbers (the ones owned by the top account) and all the other numbers owned by your subaccounts.
At any point, you can allocate a number from the top level account to any subaccount.
To do so, check the number and then, at the bottom of the table select "allocate numbers to account".
You will then be prompted to select the account you'd like to assign the number to.
To cancel numbers from a particular subaccount, you'll need to log into the account who owns the number, then delete it from their settings tab.