Recieving text on cancelled cell service

I recently cancelled my cell service and am just using my iphone for camera, games and texting my husband through my email. Yesterday I got a text from a random number. After talking to the person for a while I found out that the person she was replying to has my old iphone number. I was wondering if there is any way to remove a number and only have my email attached to the phone. I hate that I am invading her privacy by recieving her text messages. Not sure what to do about this.