Twilio was chosen as the service provider for Holonumber because of its reliable call quality and ease of use, according to Costin Miu, one of the developers behind the app. The app allows users to have a secondary line for their business without being tied to a desktop or affected by VoIP hiccups. To build the app, Costin used Objective C, PHP, and Twilio's Usage API Triggers for account balance notifications. Holonumber was successfully deployed to the App Store without any issues, offering users over 40 countries to choose from for their phone numbers. The developers aimed to provide a reliable service that would meet customer expectations, which they have achieved with Twilio's help.