Nicole Richie is hanging up on ex-beau, Adam “DJ A.M.” Goldstein -- for good. Tired of getting “constant” phone calls and text messages from him, Richie changed both her cellphone and home numbers, a source close to Richie tells Us Weekly.

“Nicole just wants to move on, but he won’t let go,” the source says. (After two years together, Richie, 25, and Goldstein, 33, split last December, briefly reconciled and then split a second time in May; she has been dating childhood pal Brody Jenner, 23, for about a month.)

Richie also told security guards at her West Hollywood condo to bar Goldstein from the building, says the source, who adds she’s considering changing her e-mail address as well. “Nicole thinks it’s unhealthy for them to talk and hopes A.M. will finally just leave her alone,” the source says.

A rep for Goldstein tells Us, “This whole story is utterly ridiculous.”

And a pal of the DJ also defends him: “If anything, it is the other way around,” the friend says. “She’s the one who calls him, and he wants nothing to do with her. He is very happy not to be with her and is dating other girls.”