That depend the plan you subscribe. Check the following link
http://office.microsoft.com/en-us/lync/lync-online-overview-and-features-online-meetings-and-instant-messaging-FX103789571.aspx
For the problem related with Lync online,it is better to post your thread In the following forum.
http://community.office365.com/en-us/forums/default.aspx
Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.
