In late January 2015, WhatsApp rolled out a limited trial for its calling feature, which allows WhatsApp users to make calls to one another right from within the app.

That limited nature of the rollout must have worked out well, because according to several different reports, the calling feature is now rolling out to all WhatsApp users. However, as noted by some reports, there are a few important details that need to be met before the feature becomes available, apparently. First, WhatsApp users will need to be using the latest version of the app, whether downloaded from the Google Play store or directly from WhatsApp’s website.

Next, and this one’s the most important, you’ll need to receive a phone call from within WhatsApp from someone who already has the function “unlocked.” Before you receive that phone call from within the app, the interface will still show only two tabs, Chats and Contacts. At some point after taking that call, though, the interface will change and there will be three tabs, as previously seen in the limited roll out, with Calls being on the far left now.

As it stands right now, it seems the only way to activate the calling feature is to get a phone call from within WhatsApp.