Michael:
These forums are for people to ask for help when they've got an OBi and they don't understand some part of how to use it - or they have problems with it. The volunteers on this site provide support. OBi also has a ticket system for customers to ask OBi for help.
OBi devices power phone service for many Voice Over Internet Protocol (VOIP) providers. Moving your phone number from your current provider to a VOIP provider, including Google Voice, is outside the OBi -and people on the forum have provided numerous posts on how to do that.
Using an OBi is not for the non-technically inclined. It is not a seamless process, there are issues, and OBi is not an aggressive customer support company. In other words, you have to have some technical bent to want to go this route, IMHO.
You seem to have little interest in a) reading, b) following instructions, or c) using the internet to lookup things you don't understand. We've provided answers to you over the past few months, and you've now popped back on after 6 weeks since you last asked questions.
You can port your number with T-Mobile (and no, their phones are not garbage), AT&T or Verizon. You've been provided with that info. It is irrelevant who your cell phone service is with today. Porting is temporary, and can be with multiple cell companies. Pick the cheapest option.
You don't know what a SIM card is. Google provides the answer:
https://www.google.com/search?q=what+does+a+sim+card+do&oq=what+does+a+sim+card+do&aqs=chrome.0.69i57j5j0l2j69i62l2.3120j0&sourceid=chrome&ie=UTF-8 Now you know.
Whatever cell company you use, when the port is done the account gets closed automatically. People use pay as you go phones. You can buy these at most stores or online. Want to use your Verizon phone? No problem. Call them and tell them what phone you have and ask if they will activate it on a pay as you go plan. There are posts all over the forum about this, including ones where I have provided a link to a cheap pay as you go phone.
When you port, you may, or may not, run into issues that you'll have to work out with the cell company. Google provides NO SUPPORT. This isn't for the faint of heart.
Have you added your existing GV number to your OBi and gotten that to work? If you can't make that work then your new ported number also won't work. And you've been told that you will not be able to have one GV number forward to the other, so this may not help you get to your final destination anyway, unless you're planning on having each GV number ring separately via the OBi. By the way, also explained on the forum is that if you setup a GV number to also ring your regular cell phone, you cannot setup a 2nd GV number to also ring that cell phone. "Forwarding phones" cannot be setup on more than one GV account.
Hope this helps.