Change you number!! It sucks to get a new number but that saved me from having to deal with my ex. I deleted him from Facebook, although he still messaged me through there and he had my email. But those are much easier to ignore than your phone.
I find it very hard to let people go as well. I did find that it was a partner that I missed and that I did not actually miss my ex.
Make a pros and cons list. It really helps when you start to let your guard down.