Can L1A individual visa holder work for a different client ?

Got a L1A Individual visa approved and stamped while working in US , then I’ve traveled back to India for 1 year. Now I want to travel to a different client (other than the one mentioned in my original petition). So is an amendment necessary for L1A Individual visa in my case ? Also my L1A Individual visa expires on Sep 2015 and my company is ready to file an extension. If amendment is necessary can both amendment and extension visa be filed together ?