Jobear9093, thanks for posting on the Sprint Community. Changing the monthly bill date is something we do not recommend because by doing so, your bill cycle dates will also have to change. With changing your bill cycle date, your next bill will incur prorated charges. In addition to that, there could be certain restrictions for accounts with a lease or an installment due to legal implications with extending the term end date of existing device agreement, and impact to monthly installment charges.
Please reply to the private ,message I sent you, so that I can review your account and see what can be done.