Does the skype iphone app cost extra with unlimited data?

I have an unlimited data plan through AT&T and I want to use the Skype iPhone app but I'm a bit wary. I was using netflix only to find out that it was charging me like crazy. Will the Skype app charge me the same way?

Hmm? You're on unlimited data. You SHOULD be fine. I don't know why you are being charged. Are you sure you on unlimited? Remember, ATT rolled out a plan that removed unlimited except for those already with unlimited data.

I think having skype is fine but charges of subscription and others must be paid!