We just built Sendchamp and I would love you to try it out.
We currently have SMS, Voice, Whatsapp & Verification APIs for developers.
With Sendchamp APIs, you can send messages to your customers via multiple channels like SMS, Email, Voice Call, Whatsapp e.t.c.
Also, we created a Verification API for you to send OTPs and Verify your users via SMS or Email or Voice call. The interesting thing is that it is free!
We also created simulators to prevent you from wasting your money while testing your integrations.
Would appreciate the feedback.