For anyone dealing with this issue, Meraki and Umbrella were unable to provide a complete solution, due to the heavy integration with Facebook. Umbrella and Meraki can block the web version, but the mobile app continued to work. I had to use a layer 3 firewall rule to block the Facebook IP ranges associated with Whatsapp. You can find them here: https://developers.facebook.com/docs/whatsapp/guides/network-requirements/
under the IP addresses section. It was a complete pain to create 230 objects and 2 object groups (remember object groups only be 150 objects max) but I have successfully blocked whatsapp completely. I know that the ip addresses may change in the future, but that is something I will just have to deal with when it comes along.