In America’s “receiver pays their part” system I wouldn’t be too sure. In the rest of the world, the caller/texter pays 100% of the charge, but in the US you’re charged per text and minutes received.

Once you add a “free call” entity on the other side (like Google Voice) then no one is charged to make the call.

Additionally, plenty of people “sell” their real number and there are android apps routing internet call through the victim’s real number. In this case, even if the person is charged, it’s not necessarily the spammer.