Yahoo! Messenger's PC-to-PC voice feature doesn't guarantee a specific quality of service. Because the data is transmitted over the Internet, we can't guarantee a specific QoS. However, Yahoo! Messenger makes every effort to give the best possible voice quality with the available system setup and network conditions.
Where's the Contact Customer Care button? With so many improvements to Messenger since the version you're using (lots more features and reliability), we figured you're ready to move up. So get your upgrade and with the new version, rest assured if you have questions, you’ll find that friendly button on its help pages.