I originally had Verizon FIOS and landline.

When Fairpoint took over several years ago, they changed the name to "FAST Internet" on the bill.

I want to move my landline to Vonage or BasicTalk because the phone is much cheaper, but I run my business at home, and depend on Internet access and associated Fairpoint email.

Somewhere I read of people unbundling their phone from Internet and when the transfer order happens, they also lose their Internet.

So I want to avoid that from happening. I emailed Vonage, and they said to check if my Fairpoint Internet uses dry loop connection without home phone service.

Is there a way to find this out without contacting Fairpoint, because I imagine when I tell them I'm moving my phone, they'll just be a big pain in the ass and not helpful?

When Verizon installed FIOS (now FP FAST) in our town they removed copper support for anyone who got the FIOS upgrade. I specifically asked at the time they offered a "free trial" period whether I could get a copper phone line back if I chose not to continue with FIOS. They said no - once FIOS is run in you will always have fiber to the house. You can't go back to POTs.

FP may have a different policy, I would bet you are stuck with FP fiber tho.

Although, to the OP's original question. I think this would just be a matter of "unbundling". You should be able to transfer your phone service from FP to Vonage and keep your FAST internet. "Dry loop" is a question for copper & DSL customers. If you are really a FAST customer then that tech no longer applies.

You should call FPs customer sales and/or retention and just confirm that you can get FAST without phone. I'm sure you can. But you may be surprised that the "unbundled" price does not make Vonage as attractive as you think it is.