One-Way Audio or “Number Not Available”

Updated 1 September 20202 min read5 steps

If you can make calls but audio is missing, or you’re getting a “number not available” message, here’s what to check.

What You Might Be Experiencing

• You can hear the other person, but they can’t hear you
• They can hear you, but you can’t hear them
• Calls connect, but there’s silence
• You get a “number not available” message

Quick Checks First

1. Restart Everything

   Switch off:

   • Router
   • VoIP device

   Switch back on:

   1. Router
   2. VoIP device

   Give it a minute before testing again.

2. Check Your Internet

   VoIP depends on a stable connection.

   • If your internet is slow or dropping, calls will fail or lose audio

Fixing One-Way Audio

This is almost always a network issue.

Most Common Cause: Router / NAT / Firewall

Your router may be blocking part of the voice traffic.

Quick test:

• Use a softphone (Zoiper / GS Wave) on mobile data
• If it works there → your router is the problem

What You Can Do

• Restart your router
• Disable SIP ALG in router settings (if available)
• Avoid double NAT setups (router behind another router)

If you’re not comfortable changing settings, log a support request.

Device or Codec Issue

• Incorrect codec settings can break audio
• Reset or reconfigure your VoIP device if needed

Fixing “Number Not Available”

1. Check the Number Format

   • Always dial the full number
   • Include area code (e.g. 021, 011)

2. Test Other Numbers

   • If all numbers fail → likely configuration issue
   • If only some fail → likely routing issue

3. Routing Issue (Provider Side)

   Sometimes the route to a specific network fails.

   👉 Provide support with:

   • The number you called
   • Date and time

Still Not Working?

Have this ready before contacting support:

• Your VoIP number
• The number you’re calling
• Time of the issue
• What exactly happens (silence, error, one-way audio)

Straight Talk

If nothing changed on your side and this suddenly started happening, it’s usually:

• Router behaviour
• Network routing
• Or registration hiccups

Not magic. Just VoIP being VoIP.