Yes, there are a bunch of alternatives but it would help if you could let us know which services you're looking for. Twilio is comprised of MANY different services and there are other companies that are focused on specific verticals. But, assuming you're thinking mostly voice/sms, here are a few:
I don't know about Plivo but if you're looking to do phone number verification we built a system for this https://www.ding.live/ with goal of improving conversion while reducing cost you can sign up there directly https://app.ding.live/sign-up.
I would be happy to understand more about what you're trying to solve don't hesitate to reach out to my email.