Is it bad manners to block a cancer charity hotline?

My mother keeps getting calls from a cancer charity, but she lost her first husband, my father, and her second husband to cancer, and she cannot afford to donate to the breast cancer research. They call harrassing her every day asking for donations. I want to permanently BLOCK them so they will stop harrassing my mother. How do I do that?

Is it bad manners to block a cancer charity hotline?
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