Best Voice Calling API & SDK Providers for PubNub

ClickSend: A simple, battle-tested SMS API built for developers. Ship messaging features in minutes with a clean API, reliable infrastructure and zero lock-ins. Why devs and sysadmins trust us: - Direct carrier routes to 190+ countries — no middleman - 99.95%+ uptime, low latency, high throughput - Billions of messages delivered globally - Pay-as-you-go pricing — no contracts - 24/7 support from people who actually understand APIs Works the way you code: Integrate via REST API, use pre-built SDKs (PHP, Python, Ruby, Node.js, C#), or trigger via webhooks. Already using Zapier, Make, or Power Automate? We've got you covered with pre-built integrations ready to go. It works straight out of the box — and keeps working when you scale from 100 to 100 million messages. No lock-ins. No fuss. Just reliable SMS infrastructure you can trust. Perfect for: 2FA, alerts, monitoring notifications, transactional messaging, user onboarding flows and anything else that needs to reach people fast.

Introducing a Real-Time Engagement Platform designed to foster genuine human interactions. When individuals can see, hear, and respond to one another, their engagement time increases significantly. With Agora, you can seamlessly integrate immersive voice and video capabilities into any application, accessible on any device and from anywhere. Agora offers a suite of SDKs and foundational elements that unlock a myriad of real-time engagement opportunities. Our network actively tracks performance, selecting the optimal routing path to ensure sub-second latency across a global infrastructure of over 200 data centers. It is designed to work with all major development platforms and is optimized for mobile devices to minimize battery drain. Built to handle sudden increases in traffic, it can effortlessly scale from one user to millions, meeting your business needs. Developers have the freedom to craft bespoke experiences through our comprehensive APIs, customizable user interfaces, and readily available third-party integrations. By choosing Agora, you provide your users with superior quality real-time voice and video, featuring intelligent routing and ultra-low latency for an unmatched experience. With such capabilities, Agora positions itself as a leader in the realm of real-time communications.

With over 700 direct carrier connections and 60+ offices on 6 continents, Infobip is a global leader in omnichannel communication. We make it our business to simplify how brands connect with, engage and delight their customers at global scale. Our programmable communications platform delivers a suite of tools for advanced customer engagement and support, plus security and authentication. We make this available to you across the widest range of communication channels possible. THE INFOBIP ADVANTAGE (1) Personalized omnichannel customer connections Achieve deeper customer engagement across the widest selection of local and global channels, including: SMS, RCS, WhatsApp, voice, video, email and the most popular chat apps. (2) Global reach, local presence Our 60+ offices around the world allow us to react faster. We provide 24/7 customer support, technical solutions in-line with needs and local requirements — based on proven best practices. (3) Full stack customer engagement Deliver better outcomes for your business by enhancing your communications with fully integrated contact center, marketing automation, and chatbot building solutions informed by our customer data platform.