The issue with calls sounds like ‘call connectivity’ issues for instance, if you receive a phone call either from internal calls and external calls – sometimes the caller is not there and you are unable to hear them.
The caller has to re-dial (sometimes more than once) but once they are connected to the person the call quality is perfect.
The issue also affects making outbound calls – it is like the call does not register the first time so you have to press ‘re-dial’ on the phone and then after 2 or 3 attempts the call is then connected.
Once the call is connected and they are speaking with the person the call quality is perfect.
Usually when we have seen this problem it is a network issue, specifically a SIP ALG on the router.
What is SIP ALG? Please click here to find out.
What usually happens is the SIP server will send an ACK (acknowledgement) packet back to the phone to say that everything is OK and the call is in progress.
It sounds like this packet is not getting back to the phone properly the first time, so the phone waits 10 seconds and then hangs up the call because it does not think it is working.
To resolve this issue you need to disable the SIP ALG on the router. You may need to contact your ISP to find out how to do this.
If you are unable to disable the SIP ALG setting on your particular model of router then please contact our Support Helpdesk we may be able to get around this issue by setting up a STUN server.
Alternatively we could provide you with a new router which we can quote you on for configuring the router and sending this out to you where once received you would just need to plug this in.
To find out more please contact our Support Helpdesk.