CallnFax Softphone – User Manual January 2026

This user manual provides instructions for using the CallnFax Softphone Android application. The CallnFax Softphone is based on the Linphone open-source SIP client, with additional security and access controls implemented by CallnFax.

1. Introduction

CallnFax Softphone is a Voice over IP (VoIP) application designed exclusively for registered CallnFax customers. The app allows you to make and receive calls and messages using SIP-based telephony services directly from your Android device.

Unlike generic SIP clients, CallnFax Softphone uses a pre-configured SIP service and requires account registration and activation before use.

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2. System Requirements

• Android smartphone or tablet running a supported version of Android.
• Active internet connection (Wi-Fi or mobile data).
• An active CallnFax customer account.
• A valid CallnFax activation license key, obtained following successful registration with the CallnFax service.

3. Registration and Activation

(Note: the app is free and is engineered to work with paid CallnFax services)

3.1 Registering with CallnFax

Before using the CallnFax Softphone app, you must register for a CallnFax account at callnfax.com.

To register:
1. Visit https://callnfax.com.
2. Create a customer account by completing the registration process.
3. Once registration is complete, you will receive an activation license key from CallnFax.

3.2 Activation License Key

The activation license key is required to unlock the CallnFax Softphone app.

• The license key is issued after successful registration with CallnFax.
• The license key may be displayed in your customer portal or sent to you by email.
• Keep your license key secure.

3.3 Activating the App

When you open the CallnFax Softphone app for the first time, you will be prompted to enter your activation license key.

To activate the app:
1. Launch the CallnFax Softphone app.
2. Enter the activation license key when prompted.
3. Tap Activate.
4. Once validated, the app will unlock and now you may complete the setup and configuration(s).

4. Account Configuration

1. CallnFax Softphone is pre-configured to use the CallnFax SIP service.
2. You will receive SIP (Session Initiated Protocol) credentials to register your app on our system.
3. It is important to keep your license key and sip credentials secure.
4. On your Android device, you will need to allow permissions for normal function, the permission needed are:
   1. Microphone
   2. Notifications
   3. Contacts
5. Optional permissions (highly recommended):
   1. Battery Unrestricted
   2. Data Usage:
      1. Allow background data usage
      2. Allow data usage while Data saver is on

5. Making and Receiving Calls

5.1 Making a Call

To place a call:
1. Open the Dialer screen.
2. Enter the destination phone number or SIP address.
3. Tap the Call button.

Calls are routed through the CallnFax network using VoIP protocols.

5.2 Receiving a Call

When an incoming call is received:
• The app will display an incoming call screen.
• You will receive a notification if the app is running in the background.
• Tap Answer to accept the call or Decline to reject it.

6. Messaging and Conversations

CallnFax Softphone supports messaging and conversation features based on SIP messaging.

To send a message:
1. Open the Conversations or Messages section.
2. Select an existing conversation or start a new one.
3. Enter your message and tap Send.

Messaging availability may depend on your CallnFax service plan.

7. Call History and Contacts

The app maintains a history of recent calls and messages for your convenience.

• Recent calls can be viewed in the Call History screen.
• Contacts may be accessed (if permission is granted) to simplify dialing.
• Contact information is stored locally on your device and is not uploaded to CallnFax.

8. Settings

The Settings section allows you to manage app behavior and preferences.

Available settings may include:
• The ring tone
• Notification settings
• The Outbound call format
• Account and activation status

Certain advanced SIP settings are disabled or hidden to maintain service integrity.

9. Security and Privacy

CallnFax Softphone includes security features designed to protect both users and the CallnFax network:

• Access to the app is restricted to registered users with valid activation keys.
• The app does not sell or share personal data for advertising purposes.

For more information, please review the CallnFax Privacy Policy.

10. Troubleshooting

If you experience issues:
• Verify that your device has an active internet connection.
• Confirm that your activation license key is valid.
• Restart the app or your device.
• Ensure the app is updated to the latest version.

If problems persist, contact CallnFax support.

11. Support and Contact Information

For assistance with the CallnFax Softphone app please contact us.

Support is available to registered CallnFax customers.

12. Open Source Notice

CallnFax Softphone is based on the Linphone open-source project. Linphone is licensed under the GNU General Public License (GPL).

CallnFax complies with all applicable open-source licensing requirements. Source code and license information are available as required by the GPL and are published on GitHub

Notice: This manual seeks to deliver the most accurate instructions possible; it is possible that errors exist. Please contact us if you have any questions.

Document Date: 1 January 2026