disconnect problem between cisco fxs and PBX seimens hicom 150

[support-ot]

 Provider => 2400 router with FXS port => PBX seimens hicom150 => internal phone

when I make a call  from outside to internal phone  and when i disconnect the call we don't have a disconnect tone on the internal phone, and the person can dial anthor number and make a call.

bellow the configuration of FXS port

voice-port 2/0
 disc_pi_off
 cptone FR
 timeouts interdigit 5
 timeouts call-disconnect 2
 timeouts wait-release 5
 impedance 900r
 station-id number 140
 caller-id enable

thanks to advice 

Karim Chaouali

[acampbell]

Karim,

Can you try adding the following to your config.

!
voice-port 2/0
supervisory disconnect lcfo
!

I am looking at this URL:-
http://www.cisco.com/c/en/us/td/docs/ios/voice/fxs/configuration/guide/15_1/fxs_15_1_cg_book/fxsbasic.html#wp1019397

Hope this helps
Regards
Alex