In other countries the caller pays for calls/texts. The way I understand it that isn't the way it works in the US (something about callers not knowing if they are calling landlines or mobile phones?)

For example, over here in Austria you can tell exactly what type of "line" a callee uses and so you know in advance how much you have to pay (even though in practice most people have unlimited calls/texts).

This means that when running a spam bot you will soon run into big issues because it simply doesn't pay off financially to send that many texts and calls.