To set up connections via interconnections between different networks (1, 2) (2, 3), in first networks (1) e.g. public fixed networks (first step), first information is received defining at least first parts of the connections within the first networks (1). In response, (second step) second information is sent to second networks (2) e.g. public mobile networks defining the charging control of at least the interconnections to be performed outside the first networks (1) and defining at least second parts of the connections. In response, (third step) the second parts of the connections are set up within the second networks (2). The connections comprise the first parts, the interconnections and the second parts. This way, ''call back'' calls can be set up without ''normal'' calls needing to precede these ''call back'' calls.