Why does family who hate and a shame of me trying to contact me?

I am a bit upset tonight as my mother contact me today. She and her husband hate me so much and a shame of me. Why does she keep trying to get in touch with me? They bring grief and anger to my life. I text her back that I do not want to do anything with them. They only want to talk to my son and I have given permission. However, they only talk to him for 5 minutes because she does not want to spend too much money on top up. This will be the last time they have chanced to talk to him. My son's success has nothing to do with them. They did not spend much effort to educate him because they did not want to spend money or invest in his life. They see money more important than family and relationship.

I have not been visiting them in 10 years because I live abroad somewhere far away from them. I do not give them a call for them every Christmas and NewYear. Why can't she understand?