Unable to Hangup Outgoing call while ringing


I installed Asterisk 11.4.0 & DAHDI Version: 2.6.2 on RedHat Linux 6. I am using Digium TE121 Single span card. And active a ISDN line from the provider.

I can call outside and can receive incoming call from my Mobile.

The Problem is : I cannot hangup/terminate the outgoing call while its ringing(only). If I terminate / Hangup the call from my IPPhone, it still ringing on my mobile. except this everything is working well.

It will be highly appreciated if anyone help on on this issue. I am spending couple of hours on this issue but still no luck. Thanks in advance.