You need to call national fuel, and talk to a person.
Give them the reading on your meter, they will re-issue you a bill right there.
It takes a couple days for it to come in the mail, and a couple days for it to get updated online.
To avoid this in the future, just read the meter during your reading window time period (ask the rep), and enter the 4 digits into the automated system.
National fuel never comes to read my meter, and if I didn’t read it myself, they would highball estimate it.
I have a 2 family house, and the upper unit is not rented out until august. They were estimating like 60-70 bucks a month for nothing running, not even the hot water tank.