I have to land line connected to mgcp cisco gateway cisco 2900 series, when client call on them the ivr work properly and the call continue.,after the call end, the line still up and didn't disconnects, when a second customer call our numbers he hears a busy line, when a third customer call he hears a busy line, we a fourth customer call he hears this line out of service after a 30 minutes the line come back and the same scenario is repeated after the second call