visual studio .net module to send whatsapp/viber messages

Hi, I'm a VBA developer working on a personal .net project and wanted to get a simple module done. I've done a bit of reading and think I need to setup bot or rest api, but just don't have the time (might need to get some help on this) Basically, I just want a function that will allow me to send a message by passing two parameters, the recipient's number and the message. not sure what's the best app to use open to suggestions but would like whatsapp or viber as those are the ones I use on my iphone.