Already too late
It's bad enough we get unsolicited SMS shit, but I've already seen spam on WhatsApp.
My father received spam from an unknown number +1 (858) 252-2319 (based in San Diego County, California apparently) with the whole crap about 'you could be due up to £(random figure out of arse generator). Contact us: +44 203 129 0785 or claim-law .co .uk' (Don't go there obviously. Googled and both those numbers and the website are known scams) Twats.
Then I went in and checked/fixed all his security/privacy settings, hopefully it won't happen again.