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Second Phone Number & Texting — iOS VoIP App with Native CallKit, SIP Calls, SMS & Automated Telnyx Setup

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Second Phone Number iOS VoIP app — native call interface with CallKit integration for seamless second line experience
Second Phone Number app — automated Telnyx setup flow for incoming VoIP calls and number provisioning
Second Phone Number app on two iPhones — VoIP dialer and SMS messaging interface
Second Phone Number & Texting is a VoIP app that gives iOS users a full second phone line – no extra device required.
Second Phone Number development challenge — building native CallKit VoIP experience with automated Telnyx provisioning
Using WebRTC and SIP, it lets users call and text over the internet, bypassing mobile carriers, while keeping the experience smooth and reliable.
Second Phone Number — WebRTC and SIP call setup with native iOS CallKit integration

The Challenge — Building a Native-Feel Second Phone Line on iOS

A big challenge was making incoming calls work for new users. Telnyx, the voice and messaging API we used, needs each account to be configured manually. Without automation, onboarding could have been slow and frustrating.
Our Solution — WebRTC/SIP VoIP with CallKit for a Seamless iOS Call Experience
We built a background setup flow that handles everything automatically. When a user subscribes, the system notifies admins via Slack and email. From there, SIP trunking, WebRTC, and iOS push credentials are configured automatically, and the account switches from “setup mode” to fully ready to use.

Users can reserve a number, manage their account, and choose the subscription plan that fits them – all from within the app.
Second Phone Number — automated Telnyx incoming call configuration for scalable VoIP provisioning
Second Phone Number — reliable SMS messaging interface with conversation threads

Automated Telnyx Setup — Scalable Incoming Call Provisioning Without Manual Configuration

New accounts are configured in the background with no delays.
Reliable SMS Messaging — Full Text Conversations on Your Second Number
Send and receive messages without carrier dependence.
Second Phone Number — phone number reservation and management dashboard
Second Phone Number — flexible number selection with area code search and reservation

Flexible Number Management — Reserve, Switch & Manage Multiple Phone Numbers

Reserve, switch, or manage phone numbers with ease.
RevenueCat Subscription Management — Weekly & Monthly Plans with In-App Purchases
Users can choose from multiple plans that fit their needs.
Second Phone Number — RevenueCat subscription management with weekly and monthly plan options

Delivery and Outcome

Second Phone Number & Texting makes managing a second line simple, fast, and reliable. Automating backend setup ensures a smooth experience for both users and admins, turning a complex VoIP system into a practical, everyday tool.
Second Phone Number — completed iOS VoIP app launched on Apple App Store with full second line functionality

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