In Germany, most call-by-call services are available only for costumers with a telephone access by the provider Telekom. Other providers tend to block call-by-call numbers. This problem occurs in many international situations as well. The rates for calls to foreign countries offered by those private providers which block call-by-call services are often significantly higher than the rates of a call-by-call-service. To use a call-by-call service, you dial a so-called call-by-call code right before the number you wish to call. You will be connected to your destination country and pay the low rates of the call-by-call service.
However, since you do not have to sign up for most call-by-call services and you do not get any immediate invoice, some customers may be unpleasantly surprised when they have a look at their invoice at the end of the month. The reason is that many call-by-call services often have inconsistent prices, which are not announced before the conversation. As an alternative to a call-by-call-service it is therefore recommended to use a callthrough service instead, especially because it can be used in connection with any telephone provider.