Modem Connections From Europe

Our sales team constantly travels to Europe, they also constantly complain about not being able to connect via the phone lines from Europe. My sales manager mentioned that our technical guy in Europe told him it is because the dial-tone in Europe isdifferent from the dial-tone in the United States. Could that cause problems while trying to connect back to the United States? If so what can I do to resolve this connectivity issue?

Thanks,
Scott