I cannot activate iMessage on my iPhone 4s.

I moved abroad and cancelled my Verizon plan, but kept my phone. Verizon sold my old phone number to someone else and I started to retrieve their iMessages. I have since turned off iMessage, created a new Apple account, signed into the new account on my phone, and tried to reactivate iMessage. However, it is still stuck on "Waiting for activation..." and says there is an error when ever I retry it. I have restarted my phone several times and waited several hours to no avail. Any ideas would be much appreciated, thank you.