In order for Sideline to give you perfect voice quality, the app uses radio towers to transmit voice signals (same as your phone carrier) to make calls. For this purpose, you will need to register a wireless phone number as a mandatory part of the account creation process.
Important: Only wireless numbers from the Contiguous United States-based Carriers are accepted at this time. VoIP (Voice Over Internet Protocol) numbers are not supported & cannot be used as your registered number.
If you don’t have a mobile number to use for registration, you may be interested in our other application, TextFree, which uses your email (or Single Sign-On such as Facebook, Apple, or Google) to register.
- Sideline is designed to be used as a second number for your mobile device and relies on your mobile service for managing communications. Therefore, you will need to use your Carrier's cell phone number when registering for your account.
- Using a Voice over Internet Protocol (VoIP) number, or a number not associated with your device will result in the inability to register for an account.
If you have further questions, please submit a request.