Thanks all, with you guys' help... I managed to get both the internet and VoiP running last night. Several things I learn :-

1. The quick setup offered by the router sucks, it won't works.
2. The default mode is PTM and it has 3 in-built settings based on this mode... VDSL_1_1, VDSL_2_1 & VDSL_3_1. We need to create a new connection based on ETH. Make sure you choose INTERNET&VOIP setting and not just INTERNET, otherwise your VOIP won't work.
3. Even when the above new setting is created, everytime I pressed "save", the router default back to VDSL_1_1. So I need to delete the 3 VDSL settings above to be able to use the newly created ETH setting I've created.

I will add more tips if required. So far, it's working fine and I can keep Maxis's Technicolor router in the closet.