I went over the number of gallons I pre-paid for my heating oil this year. In fact this is the highest amount of oil I've used in the past 5 years. Every single year it has gone down as I've "learned" the house more. Along with the bill from the oil company, I sent them this letter:

Included you will find a check for XXXX for the oil delivery that occurred on April 8th, 2009.

I have to say I was very surprised to find out that I had used up the pre-pay amount, so I reviewed my records. This is my highest oil usage in 5 heating seasons, and I am 118 gallons over the average of the last 3 years. This year's calculations do not yet accommodate for a 'final' delivery that has traditionally happened in the end of May or beginning of June.

During our yearly cleaning / inspection at the beginning of the season, I had your technician turn down the heat on my hot water heater, which I expected would help limit my usage.

All this makes me wonder if the first fill up (11/3/08) accidentally went into my neighbor's tank. The fill location is labeled left side; however there is no fill valve on the left side of my house. I attached a copy of said receipt for your own amusement.

The overrun hurts extra since I locked the price in at what turned out to be an obscenely high amount, and I am currently not generating any income.

If there is anything you can do on your end, or you have any thoughts to share on the matter, please do not hesitate to contact me.

What would the oil company do next?

A stellar customer service move would be to credit my account for the initial fill up. It would make me a customer for life.

An okay customer service move would be to not charge me for the overrun. They'd say things like "It was ~6 months ago; we may have screwed up, but don't know. You should have been watching the tank to be sure it was full every time you got a fill-up." This is kind of like splitting the difference. If they do this, there is a ~75% chance I'd stay w/ them as a customer.

A realistic business decision would be to say "It's way to late to complain about something that may have happened 6 months ago. We're sorry, but tough luck." I'd shrug my shoulders and say "whatcha gonna do." At this point, there is a 50% chance I'd stay as a customer. Could something else have cause the discrepancy?

A horrible customer service response would be to cash my check and not contact me at all. This wouldn't surprise me. 25% chance I'd stay with them for the next heating season.

Last time I had a complaint with a different oil company, the person yelled at me on the phone saying everything was my fault. I not only stopped being a customer, I filed a complaint to the BBB.

I wish I knew more. I wish I knew that they did something incorrectly. I wish I caught the mistake--if there was one--back in November.