I have a LG CU400 phone that has Yahoo, AIM, and MSN messenger services. On my plan I have 450 anytime minutes, 5000 night and weekend minutes, and unlimited mobile to mobile minutes. I also have 400 free text for $9.99. Now, with this plan, how do they calculate charges on instant messenger? Is it a certain cost to log on? Or is it a charge for each message sent and received?