Step 2: Is this a catch-up bill?
If you've had a number of estimated bills in a row and this is your first actual read in some time, that could explain why your bill is higher than usual. On your invoice, estimated meter reads are shown on the 'billed usage history' graph with an E, whereas actual reads are indicated with an A. You should expect a pattern of one estimate followed by one actual meter read.
If this does not appear to be a catchup bill, proceed to step 3.