Why can't I login to minecraft?

So I made my minecraft account back in 2011. This year, I wanted to migrate it so I could change my username. My account was working, it let me login with my email connected to my migrated account, I played with my friends, and I played multiplayer like normal. Once I went on to play minecraft, and it logged me out! I tried to use the same email that I was using before, and it didn't let me login! I reset the password, and when I logged in it said to play the demo! I want mojang to fix this, and I don't have the transaction ID or the credit card I used because I purchased it in 2011. I don't even remember the email I used in 2011, and I changed credit cards since 2011. I emailed mojang about a week ago, and they never answered. The same thing happened to both of my brother's accounts, and he emailed them a month ago, and they never answered. Does anyone have a solution to this problem? And yes I logged in with my email because it's migrated, and yes I tried my username because nothing would work and it still didn't work.