So, find out what messed up your relationship and work on it.
Were you too cranky, moody, jealous, demanding, insane, nagging-all-day, not giving him his space and freedom, disrespectful, got fat, made out with another guy, or you just sucked in bed? He needs to see that, after a month or so of breaking up, you are progressing; suddenly you became a different person. Once he sees how much different you became he'll wish you never broke up in the first place, he'll want to give the whole thing another chance too.
I'll assume you've decided that things can work out between you and him, so now, the question is – what can you do so that he believes in your relationship too? This can be a huge motivator to any guy to get back together.
As mentioned above, you need to be better than what he remembers you to be. It's important that you don't see each other for some time, and then once you do – he is just blown away by how much prettier you've become.
After he runs into you, he'll think “Gosh, she looks amazing!
Desire kicks in, and now he feels like an idiot for not staying with you.
That definitely won't help, he'll just hate you and he'll feel hurt, almost as if you were cheating on him. he has to see that you are still emotionally available for him, you just need some space and time to heal after your break up.
Hint him that you might like to get back together, but don't attack him about it. Look, if you're serious about this guy and you really want him back in your life, then you must change.
Maybe you just broke up two weeks ago and everything is still very emotional and fresh.
Either way, you can't get back together with him over the phone, so you need to see each other.