Southwest Gastroenterology Associates Pllc 525 SW 80th St., Suite 200 Oklahoma City, OK 73139 Phone: (405) 631-0481 Fax: (405) 631-9025. Office Hours: Mon-Thurs: 8:00 AM - 5:00 PM Friday: 8:00 AM - 4:00 PM Saturday: Closed Sunday: Closed.