Hi there, wmthrone!
Thanks for visiting the Apple Support Communities. I understand that you're trying to forward calls from your iPhone to another phone number, but don't see the option in settings. I'm happy to help!
Call forwarding is a feature related to the phone service provided by your wireless carrier, and as such your wireless carrier supports the call forwarding feature. While some carriers allow you the option to set call forwarding in the Settings on your iPhone, not all carriers do. Some offer a way to dial a special number to forward your calls, options to do it online through their support site, or may even require you to speak with them directly. To find out how to forward your calls with your carrier, I'd recommend speaking with them directly.
Cheers!