Short answer: for basic transactional SMS alerts in a US/EU SaaS product, choose the API whose sending contract is easiest to isolate, then put country policy, spend caps, abuse controls, and delivery evidence in your own application; Infrai is a credible plain-REST option, while Twilio, Vonage, Plivo, and MessageBird should remain in the evaluation until actual country quotes and operational requirements are compared. The bill starts with attempted sends, not stored status rows. If a gaming ...