Hey! I'd naturally recommend SignalWire (as one of the founders over there.)
We have a full messaging + voice + video APIs, including a Twilio-compatible API just for people who need to switch. We're backed by companies like Deutsche Telekom, T-Mobile, and Samsung so we know how to make telecom infra!
We're also the folks behind the open-source FreeSWITCH framework that powers companies like Bandwidth, Five9, Dialpad, Zoom Voice... maybe even your own company's PBX!
Realtime applications. Anything having to do with video & audio mixing or interaction (WebRTC, VoIP, AR/XR, NLU, Gaming, etc...) Having those as close to the end consumers as possible can dramatically improve the experience and make them far more engaging/enjoyable.
In fact, it's critical enough in many applications that clients may want to access the services in the same cloud they use /as well as/ in the same region (or potentially in their own data center.) So that means designing the systems to deploy on any cloud provider.
While this does limit the number of niceties you can use from a single provider, it allows for some pretty amazing flexibility.
Have you taken a look at SignalWire instead of Twilio? Syntax-compatible XML, less price gouging so might be able to help offset some of the costs to make these products even more affordably awesome.
I'd also love to help out on this! We power exactly this kind of voice + transcription + voice application platform stuff at SignalWire and it'd be rad if there was a way we could help get this off the ground.
Truthfully, regarding call connect charges, ringback, per-minute fees, etc... I don't think many folks think much about the fact that a lot of the business and billing decisions driving modern telecom policy are still rooted in the same thought patterns they were in the 1950s. It drives the net neutrality debates, it drives shareholder profit expectations, everything.
And I agree - it's absolutely the wild west. After 70 years of doing it one way, we're starting to see a tipping point of new realtime infrastructures and technologies. Unfortunately, I think it's likely to become even more wild as the "silo-ification of communication" trend continues. Boo.
Don't get me started on credit card processing fees. ;)
It really boils down to money. When the call connects, somebody gets charged. Perhaps both of you do -- you lose a minute on your cellphone bill, and the school gets charged a minute for the phone call.
Putting the school notice in the RBT space eliminates this charge and essentially makes the entire transaction "free."
Lots of big companies use this for the first step in their automated attendants. Since DTMF (phone number signals) are transmitted during the ringback tone (but voice is not), they can put the first step of their attendant in the RBT space. This saves them the money if you never get any further, or decide to hang up soon after.
The U.S. market for straight ringback tones was really hampered by lack of competent marketing, poor (and as josh2600 said: annoyingly over-complicated, Telecom-mentality driven) implementation, and a complete lack of inter-carrier cooperation in the VAS space. Too bad - like Indonesia, it's quite huge in Latin America and many other parts of the world.
Ring Plus is still working with that technology - but now does a lot with reverse ringback tones; rbts based on what you want/prefer to hear, not what the person you're calling wants you to hear. It's now a mobile phone MVNO in the U.S using reverse RBTs to deliver a Spotify/Rdio/Pandora-style radio feed that goes towards subsidizing or eliminating your phone bill.
We have a full messaging + voice + video APIs, including a Twilio-compatible API just for people who need to switch. We're backed by companies like Deutsche Telekom, T-Mobile, and Samsung so we know how to make telecom infra!
https://signalwire.com/products/cloud-messaging
We're also the folks behind the open-source FreeSWITCH framework that powers companies like Bandwidth, Five9, Dialpad, Zoom Voice... maybe even your own company's PBX!
https://freeswitch.com