Morning's Entertainment

I checked back with my online banking system to see if they answered my question regarding my automatic loan payment. Recall, this is an automatic payment to our van loan. In May, it was suddenly $100 less for that one month. I sent them an email asking why. This is what they said:

Good Afternoon,

Thank you for the email regarding your loan payment. We understand your concern and apologize for any confusion this may have caused. With our system enhancement the automatic payment will only pull the funds that are needed to bring your loan current. Somewhere in the history of your loan, you made an additional $100 payment. Conversion weekend took place on May 22 so when the internal transfer occurred on May 26, your minimum payment was $100 less.

Pardon me, but this is a "system enhancement"? Don't most sane people expect when they set up an automatic payment, the bank won't change it randomly? And if I want to pay an extra $100 toward the loan (given that there's no prepayment penalty), shouldn't I be able to do so without the bank undoing it whenever they want?

I responded to this. I think I'll go put the $100 back too, just to see what happens. We'll see what they say...