Call forwarding without phone, remote call forwarding

I have no idea, but certainly isn't going to get done through a customer populated forum.

This is not how you reach AT&T. And I don't know even if you do reach AT&T if it's possible to forward a VoIP landline, to a cell phone 

You can purchase a UPS unit to give you enough power to forward the phone number to another number. There are inexpensive units that furnish 10 minutes of power.  Contact your VIOP phone company for instructions. 

Assuming AT&T Phone (aka Digital Phone), there's no documented way to do so, they only tell you the "star codes" for doing it on the support site.  There used to be a website for some AT&T Phone features, but it is ancient and, I understand, unreliable and I don't know how you get to it.

Thank you everyone, I had a lot of trouble getting through to customer service and was trying everything I could to get help. I finally got through and it's something they have to do. They call forward my phone calls. 

If it's like the residential service, you can access the phone features in your my AT&T account to activate call forwarding. For the business forum click on business forum on the bottom right of this page. 

I must be losing it, I thought I posted this earlier. @JefferMC Is this what you were referring to? If so, we may need someone with the service to verify whether it's still valid. 

Yes, @spoom2 , that's the web page.  The left side "quick menu" in the video on that page had "CALL FORWARDING" as an option.