Hi, I try to use the Call Control API. So far i was testing the OMSamples programm. I added the following to the 3CXPhoneSystem.ini. Code: [ConfService] PhoneSystem.ApplicationName = OMSamples and Code: [Generall] PBXUser=myUsername PBXPass=myPass Now my Problem is as follows: Every Call using the PBXConnection throws the OperationFailed Exception. I guess it has something to do with my configurations but the exception isn't very useful to determine the error. I might think it´s a common problem but i found nothing in the forums so far. I really would appreciate your help. Thanks in advance, Sebastian Edit: I read that the API requires a commercial license of the 3CX System. I am using a demo version, can someone confirm that this might be the Problem i'm facing ? Ok problem solved, it was indeed a problem with the license.