Are you trying to make a local UK call or an international 'out of country' call from the UK? Might depend on the local carrier you're connected to and their required dialing plan. I think '00' or '+' then the country code of the country you're trying to call for an international call from the UK. That might be 'how' to call but does not cover the rates charged for the calls based on your 'international' plan on your account.