A few years ago I switched from one telephone company to another.
The phone kept working after the transfer-over day so I figured all was well.
Then I got two bills, and the old company's bill wasn't a partial month bill.
So I contacted both parties and asked them to figure it out.
Both said they were supplying the service and I should pay them.
I told them there was no way I could possibly know who was telling the truth, so they needed to work it out among themselves and let me know when they were in agreement. Until then, I would pay neither of them, since the only leverage I had over the situation is that they wanted my money and I still had it.
This went on for about 4 months.
At that point, I was tired of dealing with it.
I called them both up and explained to them the following facts:
1) One of them was telling the truth and, therefore, one of them was not.
2) I had 4 months of bills from the party that was billing me for services they were not providing.
3) As far as I was concerned, billing me for services they were not providing, after having 4 months to clear up any honest mistakes, was fraudulent behavior.
4) Since the fraudulent bills were sent by the US Postal service, that constituted 4 counts of mail fraud.
5) If it wasn't settled in 3 days I would be letting the United States Postal Service and the United States Prosecutor decide who was telling the truth.
6) I would also be contacting the relevant federal and state agencies, and my federal and state legislators, to apprise them of this fraudulent behavior.
The problem got solved in less than 3 days.
And people wonder why I resist getting my official invoices from companies via email...