My company wants me to model for advertising

Since they asked for volunteers I am assuming that you don't have to do this if you don't want to. If you choose to model I will also assume that the company would be smart enough to have you sign a model release, which generally would give them the right to use your photo in any way they see fit for as long as they see fit. Normally the photographer would have the copyright in the work, but in these situations the company that hires the photographer generally "owns" the artwork.

Ask to see the release they intend to have you sign, read it, and if you don't understand it, take it to an attorney for guidance. If they don't have one or tell you "not to worry about it", then I would decline to participate.

Since modeling is not part of your job, you don't need to help your company create advertising, and it sounds like others were asked to participate so maybe you can just say no.

As the other response notes, they'll probably ask participants to sign releases, and a release is likely to give them perpetual rights of use of the released image, as well as the right to use images you don't even like or approve. And no, since the company isn't asking professional models and has couched this as "volunteer" work, it might ingratiate you with them but don't expect to ever be paid for this modeling. Maybe you can get copies of the photos or other photos from the photographer to make this worth your while.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.