I am facing an issue with maximum simultaneous PSTN calls in our office. We are currently running CUCM 8.6 with VGW 2801 router; 8 FXO lines. All lines are working fine. At any given time, I am able to use only max 5 lines for PSTN calls (incoming and outgoing included). The 6th call onwards gives a busy tone. Attached is the VGW config.
Any advice is appreciated.