I had to go into a bitch fest at a bank once when there 'service fee' caused an overdraft on the account and I got charged 27.50 for an overdraft fee which triggered another 27.50 overdraft fee.
Almost all banks participate in this kind of practice most of it automated and frequently does stupid things like this that often go un-noticed by the average consumer.
Then they act as if they are doing us a favor by offering an 'overdraft protection' service (for a fee).
The solution is simple of course try to leave a positive balance though I know it can be hard sometimes.