This kinds of extremely minor mishaps happen all the time in large mail order business. The company simply made a mistake. They thought they had your bed in stock and so they created a shipping order for it. Your inquiry discovered that the ordering office was mistaken because of a failed communication with the warehouse.
You were not wrongfully treated. If you did not want to wait for the company to correct their mistake, you deserve to be charged the $250 cancellation fee you agreed to. You hadn't been lied to, and the representative knew what she was doing. Inventory irregularities happen all the time in businesses large and small. I spent 10 years as a business warehousing consultant, so I have seen many situations. Most discrepencies are good faith accidents.
The fault of this situation rests solely on your shoulders for not having the patience to allow the company to resolve the situation.
If you had bothered to look up Sleep Comfort with the Better Business Bureau, you would find that they have an "A" rating. In every single case of a complaint, sleep comfort has resolved the issue or offered a reasonable solution.