Hey guys,
I'm having a problem with a particular user who cannot get a proper call pickup on their phone. They were previously using an old Cisco 7940 with SIP firmware and after spending ages on decided to suggest they go with a yealink t20p.

Basically what happens is the phone rings, he picks up the receiver but can't hear anything. The calling party continue with music on hold so the call pickup isn't sent through properly. It looks to be something to do with his ISP Telstra or modem, Dynalink RTA1025WV6. When he uses the exact same phone with an am300 modem on Vodafone connection it works brilliantly. I've enabeld full access on all ports for the 2 connections.

It's funny as this has only started happening after upgrading from PBX in a flash 175x to 206x. I think the Asterisk version has changed from 1.6 to 1.8. Not sure what has changed here...?

Any ideas?