[doron2402]

That's a known issue; there are a number of companies in YC that have had to pay thousands of dollars to Twilio.

The way I've worked around this issue is by:

- Verifying the phone number before sending SMS. - Using a whitelist of supported countries. - Limit the amount Twilio can charge us

Hope that helps

[mraison]

> Limit the amount Twilio can charge us

This is unfortunately easier said than done. You'd expect Twilio to let you set a max spending limit in your account settings. Instead this is what they tell you to do: https://support.twilio.com/hc/en-us/articles/223132387-Prote... (notice the PHP snippet too)

Essentially, setting up a webhook to receive alerts from Twilio, and then calling a Twilio API to suspend the account. Your webhook better be up and running flawlessly if you don't want to go bankrupt. Why can't they do it themselves?

[citrin_ru]

> Using a whitelist of supported countries.

This may unnecessary discriminate people from countries which is not your main market and digital nomads using local SIMs. Better is to have per-country (or even per-operator) rate limits which are low by default but high for countries you have a lot of users from.

[cco]

If any YC companies are running into this, hit me up at chris ampersand stytch.com. We have a great YC deal and can stop toll fraud eating your dollars.