I would prefer for my roommates girlfriend to not always be over our home.
What is it about the girlfriend that makes you want her to stay away?
She never shows gratitude, not even a thank you for a glass of water. She is always rude to us.
It is too bad you are having trouble with your roommate's girlfriend. Perhaps you could sit down with your roommate and explain your concerns, and set limits on how often guests can be in your house.
We had a talk, but it's not working. Should I get a new phone?
Did you mean that you tried to talk to your roommate by phone, but your connection was bad?  In that case, it's better for you to have the conversation in person. Just tell your roommate that you are not a fan of having their girlfriend over so much. Maybe ask if they can hang out with their partner outside of the room more.