Kdo volal is a Czech-language community website that helps people assess calls from unknown or unwanted phone numbers. Visitors can search by number in several common formats, including local and international styles, and read comments and ratings submitted by other users. These reports may indicate whether a call was associated with advertising, suspected fraud, spam, or an ordinary contact, helping people decide how to respond.

Users can also contribute by adding their own rating or comment, sharing information that may help others recognize recurring nuisance calls. The site presents recent reviews and lists of frequently rated numbers, making it easier to browse community feedback as well as search for a specific caller. It also provides guidance on blocking unwanted calls.

The service references numbers across four Czech mobile operators: O2, T-Mobile, Vodafone, and U:Fon. With a database listing more than 15 million phone numbers and over 30,000 reviews and comments, Kdo volal offers a practical, user-contributed resource for checking and discussing unfamiliar calls