Yahoo! does not charge you to use Yahoo! Messenger on your mobile phone.

However, depending on whether you access Yahoo! Messenger through your mobile phone’s web browser or whether you access Yahoo! Messenger through text messaging, we recommend that you subscribe to a data plan for mobile web access or a text message plan from your wireless provider.

To learn more about the different access methods, see How do I access Yahoo! Messenger on my mobile phone?

For additional details about a subscription for mobile web access or a text messaging plan, check with your wireless provider.