I am wondering how to swap from telecom ADSL2+ (grandfathered 150GB total home)to VDSL naked, and port the number from telecom to WxC VFX, because the divert/call forwarding costs to mobile are too high on telecom PTSN.

I have wired up the house for VDSL (new VDSL filter, cat5e straight through to modem), and got the rest of the phone jackpoints ready to be quickly switched to a ATA. 

I want to get the free modem offer from telecom (on contract), and get the voice switched from telecom to WxC. I want to do this with less than 1 hour of downtime, what is the best way to go about this. I have read many stories on Geekzone about people being switched, and then finding out ports are not available for VDSL (or many other reasons), and then being stuck without internet, or isp / chorus dropping the ball and people ending up without internet or phone for long periods of time, and I would like to avoid this happening to me!

I may be in a contract currently with telecom, they offered us $10 off a month for staying with them for a long time, I think this put me in a contract, but not sure. What would be the best way to deal with this? 

I have never set up any VoIP, but from what I have read all I have to do is plug in the ATA to the internet and it will work.

Who should I contact, and in what order? It would be nice to get VDSL working, then switch the phones, however I guess that would mean entering into a contract with telecom, and then breaking it to go to naked VDSL? What happens if I get a number ported on a clothed plan? Any other things I should consider?