I've called the USA and it's cost me much more than normal
Elevated calling costs within the USA are down to 'non-RBOCs'. RBOCs are Regional Bell Operating Companies sometimes known as 'baby-bells' as Bell Systems, originally part of AT&T; was mandated to break up by the equivalent of the Monopolies Commission.
It's much the same heritage as the British Telecom (BT) monopoly in the United Kingdom as RBOCs service 99% of the U.S.A.
When calling a non-RBOC (similar to unbundled or LLU in the U.K) the cost is significantly more than RBOC terminated calls.
I cannot call an international premium rate number
Not all premium rate numbers are accessible internationally which is either by design by the network or by legislation.