Crankin, I'm with you about people on cell phones all the time but that is not the fault of the phone.
DDH, how old are your sister's children? If they aren't too young, why can't they wait for their mother? She's obviously training all of you very well.
Oakleaf, my SIL used to call our house, my cell, my husband's cell, my work, every number she had and leave the same GD inconsequential non-important message. I forget what we finally told her that worked but it was through gritted teeth and a forced smile. Sheesh. The other thing we told her was that we didn't take calls from blocked phone numbers so she was creating her own problem and to deal with it.
Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.