Xxsim rates info fur: Network, Make call, Receive call, Xxsim to Xxsim, SMS, Mailbox, GPRS.
World Rates XXSIM
My favorite sim and VoIP for roaming in Europe and worldwide:
UWT-mobile and Xxsim: for call+sms in Europa extern and Worldwide
ToggleMobile: for internet+call+sms only in EU intern
(VoIP/Sip) FriendCaller or SipCall.ch: Worldwide sms+call