If you’ve noticed your mobile bill steadily climb the more you use Facebook on your phone, you’re not alone. According to the website MoneySavingExpert.com, Facebook’s auto-play function for videos could be causing users to burn through their data plans quickly and incur extra charges without realizing it.

“It’s worrying that Facebook is auto-playing videos by default, as it’s clearly catching users out, with some claiming they’ve unknowingly exceeded their data limit and incurred extra charges as a result,” said Steve Nowottny, an editor at MoneySavingExpert.com.

The site says that it has received a number of complaints about the issue, and it is encouraging Facebook mobile users to change the default auto-play setting in the app. To do this, users can click on their phone’s settings, then Facebook’s settings, and then either switch the auto-play feature to “off” or “Wi-Fi only.” That way, you won’t receive unwelcome (and unexpected) data charges on your next phone bill. For more detailed instructions check out this post.

Having videos play automatically (and by default) is undoubtedly an easy way for the site to please its advertisers and make some revenue in the process. However, the goals and intentions of Facebook’s advertisers are almost never in line with the wishes of its users.