Change cellphone number harassing calls

Well you can use call blocking software. And if you are truly getting harassing phone calls you should be reporting it to the police.  

Postpaid customers can log into their account, select their phone line, and change their phone number. Keep in mind that you cannot reverse this once you've done it. There is a small fee.

And if you have anything that is too factor authenticated through your current phone number you may lose access If you don't plan ahead.