That's a toughie. I think only time will get that number out of your head and even that is not guaranteed.. it's amazing how some information just sticks there.
Rather than look at it like you need to erase the number from your mind, maybe look at what you can do in those moments of weakness to stop you dialling or sending a text?
Is there anyone who you can call to talk when you feel the urge to contact him? Could you come on here instead and maybe post? Or write everything you want to say down in a journal?
It's hard. :ghug