But you can call a mobile in Malaysia for 2p per minute and in Costa Rica for 3p per minute!................
That may be true.
The reason is because of the arrangements between foreign telcos and UK Telcos.
In the UK mobile phone companies charge BT, and other providers for access to their customers phone, in the same way as 0870. However unlike 0870, they don't pay rebates to customers. Also, because of this income the mobile companies receive, they don't charge the receiver for the call (well not yet anyway!!)
The Spanish mobile companies might be the same, and charge alot for access, and do similair deals as the UK, with inclusive minutes, and no charge to receive calls.
In America, it costs the same as a local call, and is sometimes free for the caller, but the person answering their mobile, sometimes has to pay to receive that call. Therefore the reason why in Malaysia and Costa Rica, that it's cheap to call, might be the way mobile customers pay for their mobiles and call packages as well.