I'm looking for a Whatsapp API (free or not) that let me send text messages in VB.net.

Since I have to create a Desktop Application for more than 100 PC and every user of the PC need to send whatsapp text message with its own phone number to others number, I'm looking for an API that let me subscribe a profile that let me set many numbers as "senders" with a cheap price for month

Is a service like this existing ? Or I have to create a subscriprion for everty "sender" number ?

Thanks