---
title: "International Calls Fail With A Buzzing Tone When Dialled Without A + Prefix"
slug: "international-calls-fail-with-a-buzzing-tone-when-dialled-without-a-prefix"
tags: ["Troubleshooting", "Outbound Dialling", "Number Format"]
updated: 2026-11-11T17:22:19Z
published: 2026-11-11T17:22:19Z
canonical: "docs.natterbox.com/international-calls-fail-with-a-buzzing-tone-when-dialled-without-a-prefix"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.natterbox.com/llms.txt
> Use this file to discover all available pages before exploring further.

# International Calls Fail With A Buzzing Tone When Dialled Without A + Prefix

When an international call is dialled without a leading **+** symbol, it can fail to connect and play a continuous buzzing tone instead of a normal ringing tone. This article explains why this happens and how to dial international numbers correctly so that calls route as expected. It applies to anyone making outbound international calls through Natterbox, anywhere in the world.

## Problem

Some outbound international calls fail to ring through. Instead of a normal ringing tone, a persistent, sustained buzzing sound is heard on the line and the call never connects.

Typical symptoms include:

- A steady, buzzing tone immediately after dialling, rather than a ringing tone.
- The problem affects international numbers but not local calls.
- The affected numbers were dialled without a leading **+** symbol.

## Resolution

In this scenario there is no fault with the device, the audio path, or the network. The calls fail because of how the numbers are entered. To dial international numbers reliably, follow these steps:

1. Always dial international numbers in full international format, beginning with a **+** symbol followed by the country code (for example, **+1** for the United States or **+61** for Australia).
2. Enter the remaining digits of the number after the country code. Do not add a leading 0, and do not add any local access, outside-line, or caller-ID-withhold prefix.
3. Place the call again. With the **+** in place, the platform routes the number exactly as entered and does not remove any digits.

> [!NOTE]
> ℹ️
> 
> **Why the + matters:** Without a +, the platform cannot tell that the number is already in full international format, so it applies your local dialling rules. It may then read the first digits of the number as a special instruction — such as withholding your caller ID or requesting an outside line — and remove them. Starting with a + tells the platform the number is complete and international, so no digits are stripped.

The table below shows the general pattern of how a number dialled without a **+** can be misread:

| Number as entered (no +) | How the platform can interpret it | Result |
| --- | --- | --- |
| Leading digits that match a local “withhold caller ID” prefix | Reads those digits as a caller-ID instruction and removes them | The remaining digits form an invalid number and the call fails |
| A leading digit that matches a local “outside line” access prefix | Reads that digit as an access instruction and removes it | The call is misrouted or rejected and fails |

> [!NOTE]
> 💡
> 
> **Tip:** To confirm your own audio path is working correctly, dial **1681** from your CTI to run the echo test. You should hear your own voice played back clearly, which confirms the connection between your device and the Natterbox platform is healthy.

## Frequently Asked Questions

#### Why do I hear a buzzing sound instead of a ringing tone?

When a dialled number becomes invalid or unallocated — for example after the platform has stripped a prefix — the telephone network rejects it as non-existent. The platform then plays a continuous “unallocated number” tone, which is heard as a steady, persistent buzzing sound.

#### How should I dial international numbers?

Always use full international (E.164) format: a + symbol, the country code, then the rest of the number, with no leading 0 and no local access or caller-ID-withhold prefix. For example, +1 for the United States or +61 for Australia, followed by the remaining digits.

#### Is this caused by a fault with my phone or the network?

No. In this scenario there was no device, audio, or network fault. The calls failed only because of how the numbers were entered. Dialling the same numbers with a leading + resolves the problem.

#### What is the 1681 echo test and when should I use it?

The echo test is a quick diagnostic you can dial from your CTI to check the audio path between your device and the platform. You will hear your own voice played back.

#### Does storing numbers with a + help?

Yes. Saving numbers in full international format with a leading + helps features such as Click-to-Dial route them correctly, because the number is already in the format the platform expects. This is also called e164 format and is the recommended format to store numbers, please refer to our [technical perquisites](/v1/docs/technical-prerequisites).

Computer-Telephony Integration; the end user interface / dialpad which allows the user to make, receive and interact with calls

## Related

- [Technical Prerequisites](/technical-prerequisites.md)