Looking for some advice from the experts!

Some tips:
- are you switching from traditional PBX to VOIP? Or VOIP to VOIP?
- be clear with is moving over
- gather as much documentation (product sheets, infrastructure, call routing etc.) of the old system as possible. You want to capture as much about the legacy system that the client is not thinking of. Turning off a legacy system without accounting for everything could be painful.
- are there call centers involved?
-are they changing the routing of the calls? Ring all? Round robin?
- Will you be replicating call trees?
- Don't try to cut everyone at once (10 digit dialing can be painful but necessary)
You only need to know enough to ask 'dangerous' questions. Otherwise listen to your team (esp engineering) and their needs.

I completed a smaller project—Cisco to RingCentral transition for an enterprise of 1,500 users.
A couple of learning points:
- if you can't describe what you have now, and if you can't describe exactly what you want - then you will not be able to do a real waterfall project (i.e., plan, then execute the plan). I was given "Cart Blanche" to complete this huge project in 6 months. Sometimes I pulled over 80 hours and re-read detailed vendor documentation five times to memorize all I could see so that I could be on top of the game. It was painful. Especially, that memory of well-done project is extremely short.
- establish clear Go Live. Number porting has its own rules and times when it can be done. Driving your team toward Go Live will make the difference because you will start extreme prioritization (I recommend MoSCoW)
- clearly outlining (very detailed & per person) step-by-step for your Go Live day will make your deploy a breeze. I spent five meetings disscussing, refining, and adding steps to the implementation plan.
- The biggest risk is that the deploy will flop. Create a mitigation plan to plan A. Then, create a backout plan. Then create plan B. I had no plan B because of the disruptive change of porting the numbers, so we developed a mitigation plan and a super-detailed implementation plan.
- Clearly define the risks to your executive stakeholders and mitigation plan for each. I showed them that the team forethought each eventuality - it made them feel that project is in good hands.

I completed a smaller project—Cisco to RingCentral transition for an enterprise of 1,500 users.
A couple of learning points:
- if you can't describe what you have now, and if you can't describe exactly what you want - then you will not be able to do a real waterfall project (i.e., plan, then execute the plan). I was given "Cart Blanche" to complete this huge project in 6 months. Sometimes I pulled over 80 hours and re-read detailed vendor documentation five times to memorize all I could see so that I could be on top of the game. It was painful. Especially, that memory of well-done project is extremely short.
- establish clear Go Live. Number porting has its own rules and times when it can be done. Driving your team toward Go Live will make the difference because you will start extreme prioritization (I recommend MoSCoW)
- clearly outlining (very detailed & per person) step-by-step for your Go Live day will make your deploy a breeze. I spent five meetings disscussing, refining, and adding steps to the implementation plan.
- The biggest risk is that the deploy will flop. Create a mitigation plan to plan A. Then, create a backout plan. Then create plan B. I had no plan B because of the disruptive change of porting the numbers, so we developed a mitigation plan and a super-detailed implementation plan.
- Clearly define the risks to your executive stakeholders and mitigation plan for each. I showed them that the team forethought each eventuality - it made them feel that project is in good hands.