Don't know about the orientation of your specific truck, but I know on my cummins, the compressor is probably close to two feet away from the oil pan... and even if it was near it, I'd still be very curious as to how you could damage an oil pan to the point to necessitate removal/replacement by changing the compressor. Somebody is full of you know what, got their workorders confused or something and sounds like the dealer is trying to cover it up. I can't say that with certainty, but it sure smells fishy from here. I'd be at a minimum asking them to explain how that could have happened, preferably showing me while looking at the truck. Either way, none of that pan replacement should be on your dime.