Best/Ideal SMS App

What SMS app do you all use? I need one that will send under 20 messages per month, but I need to be able to

a) send it from my text number
b) have an ability to allow a response to my number
c) have deliverability reports to make sure message was delivered

It would be nice to check if a phone number provided accepts texts but really just a nice to have.

The issue is finding a reliable provider that charges per message rather than in a bundle of messages.