That's lack of proper maintenance, which is why this thread has gone three pages without resolution. The OP said he was hard on his deck, and he is. The dealer seems to know this and did a "quick 'fix'" that a lot of lawn service guys are fine with. For some the deck should have been fixed in the slow period, for others equipment is disposable and "damage happens, run it till it dies."
It's not easy to straighten a deck depending on where the damage is, how bad it is, and the experience and tools at hand, and if the deck is used and abused maybe it's time for a new deck anyway.
When metal bends it tends to stretch, that "extra metal" can be a problem and cause a permanent bow that flexes under the pressure of having too much metal in a given area. Heating the expanded area to the critical temperature (red hot) will cause it to expand BUT it shrinks more as it cools. This is an art and of course wrecks the powder coating, and if it cools too quickly it can embrittle thin metal making the deck fragile and prone to stress fracturing. This is why for land owners fixing a deck makes sense, for a guy who hits stumps and rocks and ground mounds and car batteries and more the deck might be bashed to hell and not worth the time to try straightening it.