Please note that, there is two different aspects of professional fees;
1. Legal Fees - service provided by advocate or firm of advocate
2. Professional fees - service provided by any person in manner of technical expertise
So, point no 1 fall under RCM u/s 9(3) & point no 2 does not fall under RCM
My advise is that, please classified first that what service you have got? then easy to do taxation effect