> For the complete documentation index, see [llms.txt](https://docs.hackle.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hackle.io/en/crm-marketing/crm-properties/collect-phone-number.md).

# Phone Number Collection

{% hint style="warning" %}
**Is the estimated send count not updating even after changing the campaign's target audience?**

Check whether users' phone numbers are being collected correctly.
{% endhint %}

{% hint style="info" %}
Phone number collection is required to send Kakao Messages and Text Messages.\
Below are several methods for collecting phone numbers.
{% endhint %}

## Collecting Phone Numbers via SDK

You can collect phone numbers of users who have signed up for your service using the Hackle Client SDK.

## Collecting Phone Numbers via HTTP API

In addition to the Client SDK, you can also collect phone numbers using the HTTP API.

e.g.) When phone numbers need to be collected or updated server-side, such as in an admin interface.

## Collecting Phone Numbers via User Import

You can import all users who signed up for your service before your SDK/API integration, along with their phone numbers, in a single batch.

For details, see the [User Upload (CSV Import)](/en/user-view/csv-import.md) page.


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