My Bank is trying to steal my money, what can I do to fight them?

Here is the deal. My bank, M&T Bank, is charging me 7 overdraft charges when my account balance was positive. Here is the full details. On the 3rd, i had a starting balance of 484.60. I had 6 charges on the 3rd for about $466. According to the bank account history they provided me at my local branch, and to my online account summary, my end of day balance was positive $18.01. On the 4th I got hit with 4 $37 overdraft charges. I also had three charges totalling about $76 that posted. I realize that I should overdraft and I am ok with that, my problem is that by my figuring I should be taking 3 or 4 overdraft charges. The bank's position is that the charges that posted on the 4th were pending in the system on the 3rd, and that therefore my available balance was actually negative even though I had a positive actual balance. This is how they justify the 4 overdraft charges for transactions posting on the 3rd. They also claim that even though the only way they can justify these charges is by claiming they had already withheld the funds for the $76 in charges that posted on the 4th. They then claim that even though they held those funds already, since the transactions posted on the 4th when my balance was negative that they are also going to be subject to overdraft charges.

So the simple version, I had $89.32 in my account. I had 7 charges with a top $ ammount of $30.42 and an average of around $15, and somehow I didn't have funds to cover even 1 of these 7 charges.

These seems to me to be highly illegal. I have contacted the local branch and the corporate office and both have been dismissive and basically told me that they can do whatever they want and I just have to accept it. This is not the first time I have had issues with this bank and I not only want to get my money back, I want to make them pay for what I feel is an ongoing intent to defraud, what actions can I take?