I NEED ADVICE ON HOW TO GET MY BOYFRIEND'S EX GIRL OUT OF OUR LIFES?

WELL SHE STILL SMS & CALL HIM AND I GET THE IDEA THAT HE REPLIES.I HAVE ALL OF HER DETAILS IT WASNT EVENS HARD TO GET IT BUT WHAT CAN I DO WITH IT.I KNOW HE LOVES ME BUT WHY STAY IN CONTACT WITH HER.