A new feature available on the MyAT&T app will protect cell phone users from criminals trying to rack up unauthorized charges on their accounts.

The telecommunications giant rolled out Wireless Account Lock this week. The free feature prevents account changes, including billing updates or wireless number transfers, the company said. You can lock and unlock it at any time and it’s easily accessible via a toggle button on the user’s my AT&T app.

“If you are trying to keep any type of online account safe, here is a key point: Most attacks happen when someone is pretending to be you,” AT&T said on its website. Criminals put a lot of energy into getting your username and password. They send fraudulent emails and text messages asking you for it. They buy ads on search engines that look like links to real webpages – then ask for your password on a fake site.

“Wireless Account Lock can help with this on your wireless account,” it added.

What does the feature do?

The lock aims to thwart criminals by forcing an extra step before important account changes can be made. For example, it prevents someone from using the phone to purchase another device that the victim pays for even as the purchase is shipped elsewhere. It also prevents a SIM swap – moving a phone number to a SIM in a different device.

The lock stops unauthorized upgrades to a device or adding a new line, as well as any changes to billing information, authorized users or phone numbers.

You can turn the feature off with a quick switch, something AT&T said could be necessary in some cases.

“Keep in mind that if you select this extra protection, you may need to be available to temporarily unlock your account for a family member. They may want to buy a new device on the account or make other changes,” the company said.

Similar lock features are also offered to business and prepaid wireless accounts.