I am trying to get a voip phone set up at a colleagues house who has BT infinity.
The phone is provided 'ready set up' by vodafone one net. They provided a guide with some info such as turn off SIP alg and open ports 5060 UDP and also 1024-65535 UDP.
I have tried opening ports, putting the phone in DMZ but still no joy. I spoke to someone on the BT chat thing who said that it wouldn't be supported on smart hub so I have set up with a TP-link router and again placed the phone in DMZ with no success after opening ports with no success either. The only slight hint that it may work is that if I reboot the router, the phone is able to log in for a second or so before it logs out again. The phone works when plugged into the switch at work that all the office phones run off so one net have washed their hands of it and said that the phone is set up fine so it's a problem with BT. The only thing they said that could be useful is that some ISP's have been known to block SIP traffic which the phone uses.
I have set up a SIP circuit with sipgate which is free. And use a Cisco ip phone plugged into my router. Sets itself up with no issues and works ok. If your colleagues use the same sip provider then calls to each other are free. If you use it to call other people then just add a little credit to the account.