I just recently posted an ad on Craigslist and when I went to my email I got an email that said that I had to have a text sent to my phone for verification purposes with a code. I currently have an iPhone 6 Plus and my mobile phone service provider is Freedompop. For some reason I did not receive a code via text on my phone. I read the FAQ questions and it stated that they're are some VOIP or pre-paid mobile numbers that do not work. I need an app that will allow me to receive a text so that I can post it.
Try Ring.to. It can be used with the mobile app or in a regular web browser so you don't even need your phone. You create a new phone number with any area code so it won't be using the Freedompop number. https/ring.to/
Also, maybe try Google Hangouts if you already have a google account and a Google Voice number. I've been using that for a while and it works with many verification services. The only one that no VOIP numbers ever worked for with me was my Microsoft account.