If you're having a medical emergency, call 9-1-1 or go to the nearest emergency room. Texoma Medical Center 5016 South US Highway 75 Denison, TX 75020 Phone: 903-416-4000 Directions The Emergency Department (ED) at Texoma Medical Center (TMC) is open 24 hours a day, seven days a week to provide treatment for unpredictable injuries and sudden illnesses, including heart attack, stroke, broken ....