In V11, the default call duration is 3 hours after which it should drop the call. The variable is found in the advanced settings, custom parameters, MAXCALLDURATION. There is no way that 3CX understands the various call strings to know if local, internal, long distance or international as there is no place by which to define each. It is simply a string of numbers that we have defined to be handled in a certain manner on the outbound or as internal extension, so all are treated as the same.