I've received I think two total spam calls in the years since I ported my cell number to a voip service and set up an IVR in front that just says to press any number. It also blocks the very, very few robocalls I might actually want, and occasionally some company will refuse to accept a voip number as a cell number, but most everything just works fine.
I use voip.ms, which gives full SIP for something like $4/mo / line. Their SMS/MMS bridge is a bit limited, but I really don’t use that, and otherwise I haven’t really run into any issues.
