Academy Collections

*sigh* Okay, I got behind on a credit card at the beginning of college and I am now dealing with the repercussions. Around May 15th academy collections called me and basically went off on me. The lady who I spoke to (I have her name) told me that I needed to set up payments or it would probably go to court so on and so forth. I was ready to start making payments b/c I just got done with my bachelors and got a great job. I told her I could only afford 400 a month. I told her these payments would have to come out on the 1st or the 15th. We came to an agreement that on the 30th of May I would pay 300 dollars and then after that the 1st of each month until September I would make my 400 dollar payment. In June they charged my account on the 26th.Luckily, I had enough money in the account to cover this. They put it through earlier than the 1st which really pissed me of but my husband said let it go and so I did. However, yesterday they put through a payment of $400. I am livid! I only had about 100 in my account and so now my account is overdraft 300 dollars plus the overdraft cost. I called my bank and they said they would be sending the charge back b/c I didn't have enough in my account to cover that. I asked about how I could stop all debits from them and they explained how I could. I decided to call academy collections first and see how they would try to resolve the situation. I spoke to the woman I talked to from the beginning..She was rude, nasty, yelling at me. I told her that I had no problem paying the bill IF they took it out on the right date! She told me that she sent me a letter telling me the exact dates they would be taking the money out. I told her I didn't recieve that letter and why would she change the dates we agreed upon? I told her I was the customer and she is supposed to be the employee and her customer service skills were terrible. She said "Customers pay their bills!" I told her I was trying to pay my bill doesn't she remember recieving 700 dollars from me in the past two flipping months? She started yelling over me and said that she didn't like how I was talking to her and that since the bank is going to send the charge back to them that my settlement is off! She hung up in my face. I called my bank and told them to stop all debits from them and don't let them take anything out of my account. I AM ANGRY. I don't know what I need to do exactly. I looked up the fdcpa but I dont know where to go from here. Am I out the 700 dollars I paid them already? I really don't want to deal with their company anymore. I don't know what to do. Help!