'If it's owned by Facebook, and you use it it, so are you...'
Sadly, lots of workplaces are too useless to have proper infrastructure and so rely heavily on Gmail / Google-apps and WhatsApp etc. Especially educational institutes. Consider yourself lucky / free to escape this kind of oppression! But make sure you're not friends or have family linked to anyone in this situation sharing your cellphone / email with Suckerberg, or you're info is being hoovered up in Shadow Profile data too!