The power of words is no better proven than in the heart of the injured. Verbal abuse is no less painful than physical abuse, though the wounds of verbal abuse are invisible and un-provable. When a sister is verbally abusive to the point of even hanging up the phone during a conversation with you, the damage inflicted is deep. This type of behavior is about power and control. Take steps to prevent this behavior from happening again.
Protect yourself from your sister. Creating and enforcing boundaries is a necessary move on your part, especially when she is hanging up on you. It's not about being nice or mean. It's about taking care of yourself. Consider sending her an email stating no tolerance for treating you in this way. It might read, "I have been hurt when you hang up the phone in the middle of our conversations. I'm not willing to talk to you when you act this way. If you choose to continue this behavior I will need to end the conversation. I hope that won't be necessary." Be prepared to repeat yourself several times as a way of enforcing the boundary.
2. Assertive Communication
Assert yourself when communicating with her. Notice her tone of voice, putdowns, any dismissive attitude towards you or cursing. Be prepared to confront her the first time these verbally abusive behaviors start. Interrupt her and firmly state, "I'm not accepting how you are treating me right now. You need to change your tone and what you are saying if you want to continue this conversation." Repeating this over and over again every time she crosses the line will exhaust her or frustrate her. She needs to experience you holding the line consistently without faltering at first. You are putting in the work upfront so that later you won't have to. Consistency is the key here. Calling her out every single time is vital.
3. Follow Through
Focus on creating and enforcing boundaries. It may even be necessary for you to end the conversation with her before she does. If she is not heeding to your boundaries and continues with her behavior, you might consider saying, "I have repeatedly told you I do not accept how you are treating me. You have not stopped. I have no choice but to end this conversation. I'm hanging up now. Good-bye." Quietly hang-up the phone. She will likely be shocked. You now have her attention and she knows you are serious. Repeat this as much as necessary to take control of the situation.
4. Written Word
Insist on moving your conversations to the written form if her behavior continues. She doesn't have the right to treat you like this. Send her an email stating something like: "I have repeatedly told you I don't accept the way you are treating me. You have chosen not to change your behavior towards me. I must insist you email me if you want to contact me further. I'm no longer available to you via the phone until you can demonstrate to me you can treat me with respect." If she calls you, don't answer. Again, consistently without faltering is vital. She will get the message if you remain strong. You are protecting yourself and demanding the treatment you deserve.