My water bill is that way. If you pay online, there is a $1.99 “convenience fee” added on, whether you use a credit card or pay with your bank info. My actual bill runs around $13 per month, so it’s roughly 15% extra. Once you get above a certain limit, it’s even higher, but I never get to that point. I can’t call in to pay it though. It’s strictly online or mail a check. I mailed a check for a long time, but with only two weeks to pay the bill, sometimes the payment wouldn’t arrive until the day it was due, even if I mailed it the same day I got the bill. So now I grumble, and pay the fee.
I would understand the fee if I paid with a cc and they wanted to cover their processing fees, but there shouldn’t be any fees when paying direct from your checking account.