Sez - gst exemption

Kindly advice to me .

I have client in SEZ . I am getting service charges from client before GST i was collect service tax  client that time give service tax . after GST they are showing Integrated tax notification we have exemption  from GST.

I told to my client Itegrated tax exemption only for export not for input Tax (consume service ) GST. 

this is correct ?  Kindly advice which is correct and what i do.

Thanks.