A question about CC dispute. and VA rebate

We all know VA gone Chap11 by now. But currently I have $60 in rebate owed from VA. Since there is almost no chance of seeing those coming, so I am thinking about disputing the charges at my CC company which is At&T Universal mastercard. I made 2 purchases at VA on 6/23 and 7/1. And I payed those in the monthly CC bill already. So I am wondering if it is still possible to dispute those charges if I have already pay the bill? And is it possible to dispute charges because of merchant went chapter11 and cant pay rebate? Thanks for any information anyone can provide. letian ------------------ letian