I'd recommend not talking to him anymore. Apparently your words aren't registering with him so don't waste your breath anymore. Do you have caller ID on the phone? don't answer it when it's him calling. No caller ID? get an old fashioned answering machine that lets you hear who's leaving a message, and screen ALL your calls this way. Don't pick up if it's him. Don't talk to him. Don't give him any money. Don't give him any reason to think he might get money or shelter or food or even sympathy from you. No contact at all is probably best since he doesn't believe you when you say No.
Give him Nothing. Not even the time of day. Anything he gets from you, anything at all, even just your listening to him, will give him hope.
Stay strong! we're rooting for you.