H1 visa under 221(g) blue slip ..h1 petition experience in Sep2017


#1

Attended h1 visa interview at Chennai and received 221g blueslip asking for updated client letter A.
My approved h1 petition expires in SEP 2017.
Current client A is not providing updated letter.
Meanwhile, other client B is ready to provide client letter.
Can we change client letter now?
Can we request for h1 extension with new client letter, please suggest.

Please note H1 approved petition expires in September 2017, get least time frame to react.