@factsdontcare, just a heads up, Google Voice is not allowed. That's what I have had on my phone for years including when I signed up, and OU has now determined that it's no longer allowed.
@Casperdiddle, @revtrust , I had the same problem. Not only could I not reply to people responding to my listings, but I could not make any changes at all to my account after OU suddenly decided it didn't like my phone number. That means not being able to change my phone number, not being able to delete my listings, nothing! It had become read only.
As I had explained this to CS, their only suggestion was to buy a phone/service with an acceptable number. I told them that if they couldn't fix my account than they should just delete it. So they deleted it. 2 1/2 years a member, 5 stars, and excellent feedback, and their choice was to delete the account. Maybe if enough people with good ratings delete their accounts, OU will wise up and stop some of their changes that make the experience worse, or punish people for not complying with their unannounced whims as this phone verify is.
The Terms of Service says I must maintain correct information on my account, but they locked my account for verifying the same information I used when I created the account 2 1/2 years ago. Now they want me to get another phone number for the purposes of verification? Doesn't that go against their Terms of Service?