api_or_ipa parent
My cellphone plan gives me unlimited SMS but only 2 gbs of data. If unlimited really means unlimited, then my data comes to me for free (assuming I was going to keep my sms package regardless, which I am).
Unlimited never means unlimited. It means the seller of the service thinks there's an effective limit to what most customers can consume and he thinks he can provide more than that for a flat price.
This generally works out well until people figure out creati e ways to consume levels of service beyond the effective limit -- then the service provider is oversold, and it's either underdeliver or invest in living up to new demand (probably financed with a price increase).
See also "salad stacking".