I would lay it on the line in one more email.
"I received your last email and honestly, I've been stewing about it, because really, how do you respond to a parent's email that only says, "I hate you"? Since your, "I hate you" was very blunt, I will in turn be blunt for you: I have been delaying calling you on the phone because I dread being yelled at and berated on EVERY SINGLE CALL for merely living my life further away from you than you'd like.
Yes, this happens every time we speak on the phone, and honestly, it makes me want to contact you even less. Think about it...why would I want to do something that will invite someone to yell at me? You may be my parents, but I'm an adult now too. I won't put up with that. You don't make me miss you when the contact we do have involves yelling and guilt trips.
So with your last message to me of "I hate you," I think it's best that I take those words at face value, because really, WHY would you say something like that to your child, who you supposedly want more contact with, if that statement wasn't true?
So I will be operating under the assumption that you hate me and wish no further contact. Likewise, I will not contact you. This is best right now, considering the emotions on both sides. I may contact you at some future date to see if your feelings for me have changed, but right now I don't know when or if that might happen.
I think you need to call him/them on the "I hate you". Notice I brought it up several times. They have to know that they've crossed a line and they can't just jump back over it.
Have you considered getting a different cell phone number?
Good luck to you.