[Freeswitch-users] playback results in silence

Hi, we use mod_nibblebill and want to play a wav when the low ballance amount is reached. We noticed alreday that the example in our nibblebill.conf.xml 'play ding' is not working. There is no application play and no file ding. We use now 'playback misc/sorry.wav' for testing. We can see in the log that the file is played and we can here a silence during the playback of the file, but not the voice. If we build a small dialplan entry with 'answer', 'playback misc/sorry.wav', 'hangup', we can here the voice. Any ideas? Best regards, Bernd