How do i contact keystone health services? Contact us By mail. Keystone First 200 Stevens Drive Philadelphia, PA 19113. Driving directions. By telephone. Main telephone number 1-215-937-8000. Member Services 1-800-521-6860 TTY: 1-800-684-5505 Representatives are available 24 hours a day, 7 days a week.Why get in touch with keystone? Get in Touch. Keystone is for people who believe that powerful partnerships generate prosperity. We band together to safeguard what matters most and provide peace of mind in the neighborhoods and communities where we live and work. With Keystone, independence works better together.Who is keykeystone for? Keystone is for people who believe that powerful partnerships generate prosperity. We band together to safeguard what matters most and provide peace of mind in the neighborhoods and communities where we live and work. With Keystone, independence works better together.