First, whenever you file a fraud claim against a transaction, make sure that you follow up any telephone calls with something in writing. If you look through your account terms there should be a section in it that explains the process and where to send your writen claim. This does two things. It preserves your rights and it starts the clock ticking for the bank to resolve the complaint.
In most cases, if a bank does not receive your fraud claim in writing with a certain period of time (I think it is 10 days but your account terms should tell you) they will deny the claim and reverse the provisional credit.
You should have or will receive a letter from the bank telling you the claim was denied, why and when the provisional credit will be reversed.
If the claim was denied for any other reason other than a failure to submit the claim in writing, you are able to request copies of the documentation the bank used to investigate.
As to your overdrafts. It really is simple. Don't initiate transactions until the funds are available to draw against. Again, read through your account terms. There will be a section in it that explains the bank's funds availability policy. There should also be sections in it that explains how they process check card and debit transactions. Depending upon the type of deposit (check, cash) determines when the funds become available to draw against. Floating transactions is a sure fire way to set yourself up for overdraft fees. Paying a late fee to AT&T would have been less of a cost than floating their payment.
In general, with check card purchases or payments, the funds for the transaction are placed on hold (though not deducted from you running balance). That means that the rent check when presented to the bank may not have had suffcient clear funds to pay it, due to the hold of funds on the AT&T transaction you initiated at 11:00 AM. Thus the NSF fee (which would have shown up on Monday) plus any other debit card transactions initiated over the weekend, and their associated NSF (which should have shown up on Tuesday). By trying to float the AT&T payment, you set into motion a cascade of overdraft charges that you could have avoided.