Lynne, maybe you can give some details, but the usage of Skype is not going to cause you any problem with 20 gigabytes to access it. The cap comes in when you have heavy video or play three-dimensional games, or something like that. If you use it for Skyping, you will not use anywhere near the 20-gigabyte cap.
On February 3rd, 2011. See this statement in context.