What is the best web service to call a mobile phone (send notification)?

Question

speech synthesis

Suggest a web service that could be used to call a mobile phone, read a short notification (text2speech), and then wait for a keystroke from the subscriber (a simple IVR).
I actually found several such services:
www.twilio.com, voximplant.com, www.nexmo.com, www.cdyne.com. Prices from 0.14 to 0.6 $ per minute for Ukrainian mobile.
There are even more services that seem to be doing something like that, but I have not yet figured out how and how much.
Interested in the impression of people from using a particular service (not necessarily from those that I have listed). I need to choose one thing, I'm afraid to make a mistake with the choice.

Answer 1

Build it yourself on an asterisk.
You can choose your own operator. At least install a GSM gateway with unlimited tariffs.

Answer 2

I advise you to assemble it yourself (you can use freeswitch js), all these services have per-minute billing.