Bad news is that this needs to go to a repair shop. It'll probably take a refinishing after the dents are removed. They may be able to use the set of magnets I saw for doing this sort of thing, has graduated sizes of RE ball magnets and one padded and curved magnet for moving them around. They cost more than a new trumpet, so not something for a one-off fix. It also looked like it would take a skilled hand to do it and not end up with a stretched-out mess.

Stan