I agree with you, I’m not sure how you would know if someone were using a VoIP phone or not.
I was on VOIP engineering team that installed Voip phones at every location of Bank of American in the USA, some of the other companies I’ve installed VOIP phone at are KPMG, Capital One Bank, and Exxon-Mobile.
From the description, transferring number from legacy voice systems to Voip System is very normal and done all the time.
Legacy systems like Fax Machines can be configured to use VOIP systems, in big companies, we converted dozens of fax machines to a Voip system.
I’m thinking the poster doesn’t have all the information or understand what the issue is.
All I know is what they’ve told me. One place even had an auto reply stating the reasons they couldn’t accept my account setup; and one of them was ‘You are using a VOIP’.
Again, when this has been a problem (three times) we have been able to rectify it; but not without wasting time on phone calls and, in one case, having to contact them by snail mail.
I’m dating myself a bit, but I use to install T1s and cisco IP phone systems for Telesphere before they were bought out by vonage for business... Large (I’m talking 500-1500 phones with multiple T1 or larger feeds) offices used them. VOIP is much cheaper than POTS lines.
“I’m thinking the poster doesn’t have all the information or understand what the issue is.”
ditto ... namely because almost ALL phones are VOIP these days ... copper land lines are deader than Dodo birds ...