Twilio's new Verify API is currently available as a Public Beta product. Some features are not yet implemented and others may be changed before the product is declared as Generally Available. Public Beta products are not covered by a Twilio SLA.
If you already have token generation and validation logic and would like to keep those systems in place, you can do so. We have a feature where you can submit your code to us and utilize our pre-screened message templates and localizations for both text and voice.
With this modified setup, you will be charged on each attempted customer verification (requests for a verification code). Due to situations like abandoned requests and users who eagerly request multiple codes, we typically see 30% more verifications starts than verifications checks. This means that you can expect to pay 30% more for this feature. Keep this in mind as you are considering your options.
If you're using custom verification codes you must also provide feedback that lets us know whether or not the user verified the code. This allows us to proactively monitor our global routing and stay operational.
Contact Twilio Sales and we'll help you enable this option.