I also highly reccomend Ebay or Kijiji. Ebay has a guarentee or your money back that you get what you paid for, and it's alot cheaper than factory refurbished. I have had a great experience with Kijiji.
If you are using an iPhone, there may be a setting you forgot to change. If that is the case going into settings > Messages> Send & receive and check that your new number is there
