No and that is why WhatsApp should not be used in an organisation.
WhatsApp is a product of Facebook and Facebook is certified under the US-EU Privacy Shield. So theoretically transferring data to Facebook resp. WhatsApp would be permitted.
In their licensing conditions WhatsApp asks for permission to upload all saved telephone numbers and contacts from the mobile phone to Facebook/WhatsApp. Without this permission WhatsApp is not useable. The data is being used to identify familiar persons.
The problem here is that thereby the data from third parties is also transferred to Facebook, even though the third parties may disapprove of that. That can directly affect these persons because of the established connection from your and other address books, which is undesirable.
Another problem with WhatsApp is that the usage is almost inevitable in the private sphere (especially for groups in clubs, classes, …). Once you are using WhatsApp in private your business contacts will be transferred to Facebook as well.
Please notice, using WhatsApp is data processing according to GDPR. Therefore, you have to document this in the records of processing activities. The simplest way to create your record is easyGDPR.