I am getting a busy signal after dialing '11' for internal calls to extension '112' and any other extension beginning with '11'. Busy signal occurs immediately after dialing the second '1'. If I press "New Call" dial the extension then press "Send" the call goes through just fine. That is, dialing WITH a present dial tone fails. Without dial tone present it works. All of my extensions are 3 digits and as far as I can tell I have no special extension numbers beginning with '11'.I'm using 3CX version 12 for Windows and Polycom VVX 310 phones. Any ideas? Thanks.