AIU Online charged for classes I did not take and didn't receieve material for Internet

I attended school with them and I withdrew from the school followed all their rules and regulations on how to withdraw from school. I emailed my academic advisor and request to be withdrawn from school. I thought that it would be over and that it would be taken care of off. Imagine my surprise when later tried to get my transcripts and was told there was a hold on my acct and i couldn't get my transcripts because they charged me for the next semester which i withdrew from and never received books for. Can anyone tell me how i can dispute this balance and obtain my transcripts.