Are there any services that allows you to port your current fax number to them?
I suppose it is possible, but I doubt it.
Been a while since I checked out the various services (mentioned above and a few others), but all of them had numbers in a "bank" that they would assign to you.
You can get a toll free number of your own and point it to the service if you wish. That way if you fire one service & pick up another it is no big deal.
But be aware of a potential problem. I had a toll free number that pointed to my Maxemail number. For a long time everything worked fine then I stopped getting some of my faxes. Others would come thru but only partially.
After talking with Maxemail I found out that ISP based fax services don't always play well with VOIP long distance services. I went back to giving out the long distance number in Chicago and have not had a problem. For less than $40 per year I get all the fax services I need. I can get a toll free, or even a local number from Maxemail (something that was not originally available) for a higher price. Many who communicate with me via fax are out of the Atlanta area any way, so I see no need to pay extra for a local number.
Anyone that really needs to send me a fax has not complained about long distance, so it works well.