Many people use their personal phones for work calls. They may have inadvertently breached NDAs, and in some cases laws, by not paying attention to their privacy settings.
No offense but if you have an NDA that can be broken by using your personal phone you probably shouldn't use your personal phone to make those communications.
> if you have an NDA that can be broken by using your personal phone
Almost every NDA, including those standard with employment packages, include in the definition of confidential information the time, date and duration of phone calls with customers and sensitive suppliers. Anyone in a customer-facing role would thus be required to keep those data confidential, i.e. not disclose it without proper authorization to a third party, e.g. Facebook.
This might work for an employee defending against their employer. It wouldn’t work for the employer relative to their customers; or a contractor to their clients; or any other situation. In any case, my point is Facebook may have caused many people legal harm.