I do not believe they charged me for it, but they mistakenly sent extras of an item I ordered. Do I need to return them?
If the company is mostly owned by non-Jews, then it is only an issue of returning a lost object to its owner, and here you are not obligated to do that. If you want, you can call the company to make a kiddush H-shem and tell them that you got these extra items, and you are Jewish and you don’t want to take something that isn’t yours, therefore you want to know if they want you to send it back (at their expense).
If they say to send it back you can, but they most probably will tell you to just keep it.
Rema CH:M 348-2.