Urd interstate transaction done

Hello Experts,

Greetings for the day!!!!

What if and Intertrasactions done between URD and RD.

Example: One of My client is stayed in Bihar and vendor is from West Bengal, 

he took service in Bihar and same purchase invoice booked. but by GST LAW its wrong transactions. 

please advice what will happend in this case. and suggestion for the same. 

and also 

what if the the service is under RCM with same vendor and same state.

Looking forward for your reply.