This was SUCH a headache to resolve. I feel like it's my duty to post what finally worked for me. My issue was I left my 4s phone on the roof of my car and it got run over (classic blunder). I was still able to plug it in to charge, but the screen was completely crushed and unworkable. My upgrade with Verizon is just a few weeks away so I opted to use my husband's old LG phone in the meantime. After taking it in to the Verizon store and having them activate it, I still couldn't receive texts from anyone who used to imessage me.
First, I deactivated the device from my account on itunes and deleted my phone number from the account as well, as others mentioned. Still couldn't receive texts from imessage users (I could hear the text being sent to my old, crushed iphone). I then tried signing in on my husband's phone under imessage settings, deleting my email and phone number from the "receive at" option, and turning off imessages. Still no dice. What I finally had to do was plug my crushed phone in to my pc, connect it to itunes, and choose "Restore iphone". Before I restored it, my phone number was still showing up under the summary tab. After the restore, the phone number space showed "n/a". Apparently this was the last link, because I'm now receiving texts from all again.
Hope this helps anyone else who's frustrated!