Y’all quit downvoting OP. He’s right in some cases, not so much in others.
US here, old cable internet guy. Can’t speak for all the ISP’s, but the several I’ve worked leave your dynamic IP alone unless you swap routers or modems. Weird because they used to swap your IP on reboots, or seemingly randomly. 🤷🏻♂️
Can’t think of an easy, reliable way to do it without new hardware.