To do so, you'll need to create an account and log in. After you make a request, we'll contact you to confirm your appointment. Visit the AG Patient Portal to schedule your appointment. If you need assistance with our patient portal please call 512-579-2656 or email PortalManager@austingastro.com. Billing. Phone: (512) 420-0186 Fax: (512) 420-0397.