new H1b amendment while one is in progress

Hello,I am in a situation could anyone please provide some guidance,I was working with Client A till March End 2018 on H1b – (with H1B approved till Nov 18 2018 with client A),but my contract ended with Client A and I moved to Client B with the same employer, my employer filed a new H1b extension/ amendment, but now I got a call from client A asking me to join back, if I move back to Client A, and file new H1b amendment , can It be denied since one h1b amendment with client b is already in progress. and I am already working with Client B from April 2018 until now.can I withdraw the h1b amendment application from the client B and start working for client A? again by filing a new H1b amendment with client A?ThanksAditya