Gst exemption on tele radiology

I am a Teleradiology Company, we receive images X-Ray, CT,MRI etc from Imaging centers online and send these to Radiologists for Reporting. These reports then we mail it back to the Imaging Centers. 

We bill the imaging center for this service. Also the Radiologists bill us for their reporting service.

Both the Imaging center and the radiologist are exempted from paying GST . Do we have to pay the GST and on which amount. Please clarify.
Regards
Navin