Change account "full name"

My preliminary response is "No, you may not"; however, to echo similarly-expressed queries: May I ask why your Billing information is presently listed in that of your mother's name?

The account to which you are referencing must remain in your mother's name until you have reached the age of 18, or—depending on your place of residence—become of legal age; at this time, you are welcome to contact Billing & Account Services to have the matter officially addressed, as shared ownership of the account would then come into question.

Please note, however, that access to an account is restricted to one adult and one (1) minor child. Given the details you've provided herein, it may be beneficial for your mother to perhaps set up an additional account for your brother, as this would ensure that all policies and rule sets are being upheld. :)