Yeah, we have this issue too when playing with the clan. It doesn't matter if you set a push to talk key in Origin, you'll still hear their microphone.The only thing that can be done is to either reform the group and hope it's enough, or just leave the group when you have joined the match.
I'd like to bump this up as it happened to me and four friends yesterday (Ewok Patch). I must add that it was very annoying, as it seemed for every new member added to the group, someone would gain or lose the ability to mute someone else, be it the newcomer or someone already in the group.
We were five, and it had funny situations like player A only can't mute B, and B only can't mute C, and C only can't mute A. Players D and E were unaffected. Or things like player C only can't mute players A and B, but both of them can mute everyone, player E only can't mute player A and player D only can't mute player C. Also, like I said previously, imagine players A, B and C are all in the group, but B can't mute C. Then D joins. Suddenly B becomes able to mute C, but C loses the ability to mute B, and D joined unable to mute A.
It was a big mess, and we resorted to origin calls to mute every microphone in-game. Whenever you start a call with someone on origin, it mutes you from everyone else in your group, and mutes everyone else in your group to you.
