Twilio
SMS, voice, and verification — one-time passcodes, OTP login, and text notifications sent from your app.
Why we need this
Twilio is the service that sends the SMS and voice messages your app relies on: one-time passcodes, phone-number verification, OTP login, and text notifications. Calda connects to it through the Twilio API (and the Verify service for OTP) so the app can send messages reliably from a number that belongs to you.
Like all other accounts, this one should be owned by you. Your phone numbers, A2P/sender registration, and messaging history are tied to the account, so keeping it under your company means those numbers and that sending reputation belong to you, not us.
Do I need a credit card?
Twilio gives you a free trial with a small credit to test sending, and that trial requires no credit card to start. The trial is limited, though — messages can only be sent to verified numbers and they include a "Sent from your Twilio trial account" prefix.
To send to real users, buy a dedicated phone number, and complete sender registration, you'll need to upgrade to a pay-as-you-go account, which does require a credit card and a starting balance.
Heads up before launch
US and Canada SMS now require A2P 10DLC registration (or a toll-free / short-code path) before carriers will reliably deliver app traffic. Registration takes a few days and needs business details, so plan to upgrade and start it early rather than right before launch.
Step-by-step setup
Create the Twilio account
Sign up at twilio.com/try-twilio using your company email. Twilio organizes everything — phone numbers, messaging services, API keys, and billing — under your account, reachable from the Twilio Console.
Buy a phone number
In the Console, go to Phone Numbers → Manage → Buy a number and choose a number with SMS (and Voice, if your app needs calls) capabilities in the country you'll be messaging. This is the number your app's messages will come from.
Verification (OTP) doesn't always need a number
If you only need one-time passcodes, Twilio's Verify service can send them without a dedicated number. We'll set that up on our side once we have access — you don't have to decide this now.
Complete A2P / sender registration
You'll need your business details for this step — legal company name, address, and website.
If you're sending to US or Canada numbers, open Messaging → Regulatory Compliance / A2P 10DLC and register your business and a messaging campaign. Carriers require this before they'll deliver application traffic, and approval can take a few days.
Invite Calda
Open Admin → Manage users (the account menu in the top-right), click Invite user, enter the Calda email we share with you, and grant the Administrator role. Admin is required — it lets us create the API keys and configure the messaging service that sends from your number.
Confirm in Slack
Don't forget to notify us in Slack so we can accept the invitation and confirm that we can sign in.
Conclusion
That is it — with this configuration we can start sending SMS and verification messages from your number. Once you've granted access and confirmed in Slack, we'll handle the rest of the integration on our side.
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