Twilio[1] and MessageBird[2] come to my mind as competitors. They both are a "Voice & SMS" communications platform and I guess the innovative part is that they provide an easy way of connecting companies to their customers via multiple channels.

[1] https://www.twilio.com/ [2] https://messagebird.com/en/

Don't forget about Nexmo, which was purchased by Vonage. We have been using all of those companies (and others) for years at https://www.engagespark.com , and they all have pros and cons / strengths and weaknesses. Infobip excels in some areas and stinks in others; same with Twilio and Plivo and Nexmo and MessageBird. That said (and this is no plug, just based on experience), Nexmo has been the most reliable by far and has consistently offered the best support across the industry.

Sweden-based http://www.sinch.com as well.