Apparently it is no longer allowed. I have used magic jack with Xfinity for several years. Two days ago my phone stopped working. After hours of trouble shooting with Magic Jack and then with COMCAST, it is still not working. COMCAST says I will have to use an entirely different phone number bundled with my Xfinity service. Of course I am not happy, I have had my number for 30 years always porting it when necessary to my new provider (ATT, Verizon etc.).
What is going on, I thought I was using VOIP with Magic Jack and it should work with any ISP.