You don't want him back, tangie? and something tells me you don't *wink* well then, tell him politely that it was nice to hear from him but you're asleep/partying hard/out with friends/in the middle of dinner/WHATEVER as long as it looks like you are having fun without him
And if you can't be bothered talking to him at all.....go the caller ID, as Miss Cowboy has already mentioned
and ignore the bastard.