Because he doesn't really want you to be totally out of his life. I bet that he still wants to be friends. Just not as serious as you were before or he just wants to have a mating partner but that is the least likely answer
cos she's still into you.
Give him enough space to make a decision. He's not over her.
he's not over you and/or the relationship itself
Answer the phone and simply tell them that you're no longer with said ex, and to stop calling you or contacting you.
Maybe they don't want to lose the friendship you both had with each other while you were both in a relationship. There's always this bond that may have been between you two that the person may not want to lose. Or maybe the person hasn't yet completely got over you. But if you don't feel comfortable with your ex contacting you still, let him/her know that.
If your ex still has feeling for you then they will try to contact you and if they don't then either they may feel the relationship is truly over and you may have to run the risk of contacting your ex and try to meet somewhere to see if there is anyway you can salvage your relationship.
Just think about other things...don't keep your mind on it.
If your ex is over you they would have stopped contacting you or, you may have heard they are either dating or into another relationship. If your ex is still not with someone and contacts you on and off he could still miss you. If you feel he does miss you and you still care about him then see if he will meet you somewhere privately and discuss whether or not you both want to try at your relationship again.
he might want to stay friends, or more likely if he keeps contacting you he cant let go.
If you want to move on the best thing to do is cut all ties, keep your distance and leave him in the past and move on.
because he either misses you, or else he wants to slowly test the waters to see if theres anyhting still there between ye, so ye can either be friends or try again.
Probably best not to, if yoou want to keep your friend. Just keep mutual-acquaintance with your BF's ex until she is totally over him, or circumstances change- then, go for it!