IGST or CGST and SGST ?

First of All if you are providing services to Registered person then either you have to charge 12 % (As per Notification 22/2017 CT (r)) Or As per Section 13/2017 CT (r ) Nil GST , because your services is cover under RCM & Recepient is liable to pay GST

& If you are providing Services to URD then your services is exempted As per Notification 32/2017 CT (r).

** it's Notification 13/2017 CT (r)