If you receive a call that starts with this seemingly innocent question, hang up immediately, the Federal Communications Commission warns.

Scammers are increasingly using this phrase to record the word “yes” from unsuspecting consumers. Later, the recording can be used as a voice signature to authorize charges on the victim’s utility or credit card account.

“If you receive this type of call, immediately hang up,” the FCC said in a consumer advisory note issued Monday. “If you have already responded to this type of call, review all of your statements such as those from your bank, credit card lender, or telephone company for unauthorized charges.

The practice is known as “cramming” and is becoming more prevalent. Last week, FCC Chairman Ajit Pai published a column on what he called an “explosion” of robocalls. He reports that American consumers received about 29 billion robocalls in 2016—or roughly 230 calls per household.

The FCC urged consumers to report unauthorized charges to the Better Business Bureau’s Scam Tracker and the FCC Consumer Help Center.