Change of name

I went into a Telkom office to change my dad’s account which is in his name to my mom’s name as my dad is in frail-care and would not be able to do it himself. Went there with both their id books and mine as well and was told that my mother of 93 would have to be present of that they can take her “THUMB PRINT”. What in the world would they need a thumb print for just for a name change. I think it is ridiculous.