I had the exact same problem where TWC kept responding to VOIPO indicating my number didn't exist. I get the feeling they (TWC) dragged it out to get a couple more billing cycles out of me before porting the number. I must say the few bucks they got out of me will ensure I never return to their service.

I escalated within VOIPO tim at voipo dot com who assigned a representative to the case (a gentleman by the name Christopher G. who I reached by sending email to support at voipo dot com) who first called me to understand the problem and made every attempt to move things along. Christopher also sent me weekly updates concerning the issue and was very responsive to my queries during the entire transfer. All in all it took about 2 full months to finalize the transfer.

Thus far, the phone has been working perfectly after the transfer was complete.

Definitely get Tim and Christopher G. in the loop on this.

Hope it works out for you.