To Airbnb's credit, they do have excellent customer service. I had trouble listing my place at first and when I contacted their tech department, a human emailed me back. I thought that was pretty neat. I did end up with two listings after the confusion regarding the first one. I can't remember if they contacted me about it being inactive. It is inactive though and the second account, which I do use, is in serious neglect. It's possible this is a valid number, but like any random call -- it's best to check the source directly before returning the call.