why are 0800 numbers not free on mobile phones?

Answer 1

On a mobile phone you are paying for airtime essentially. The phone companies have it rigged so both the sender and receiver pay, so in effect they double bill every call. The first so many hours or minutes are covered under whatever calling plan you have, and if you never exceed the maximum for that plan it costs nothing extra for the call. What happens in that case is you pay for calls you do not even make, which is worse than paying for a free call.

Try to figure this out to much and you will drive yourself nuts.