Group messaging iphone 4s ios7 not working

Hi guys, my group messaging is not working. I browsed the other discussion and did everything people recommended (turning of and on phone, turning of and on settings for both group mesasges and MMS messages) but nothing is working. I sporadically somtimes get the group messages that are sent in the group but more often I do NOT get them, and in addittion I cannot send any group messages in the group. I have 4 people in the group 1 of them has iphone 4 with ios6, one an ihpone 5 with ios7 and one an android phone and for ALL of them it works but just for me it doesnt. Also the person with the iphone 4 wiht ios6 has the exact same AT&T plan as I do and it works for her so I figured it cannot be that.

Any more suggestions about what to do before going to either the ATT store or the Apple store?

Thanks!