Mercy Clinic Primary Care - Medical Tower A Suite 399. 621 S. New Ballas Road, Tower A, Suite 399 St. Louis, MO 63141. Phone: (314) 251-1820. 1699.3 Miles. Select. Select a Visit Type. To ensure the highest quality patient care, please select the most appropriate visit type, as length of visits vary. If you do not see your visit type, please call..