These scammers don't care who they call. Tell your mom, if she can, to not answer calls from unknown numbers. I know it's not always possible; my senior Mom has to take calls sometimes that she doesn't recognize due to various medical officers needing to reach her.
Did not leave message, calls 2 times/day. Caller ID sometimes says United Breast Cancer, CCI, or phone #586-482-8704 or 586-210-9022. Never ever answer my landline. How sad.