I was Nee Naa for quite a long time to my first GC (as was any vehicle with a siren, and his best little friend) until he finally managed Grandma.
His little sister, now 6, normally calls me Grandma, but for the last couple of years has occasionally called me 'Granny', just to see what reaction it gets - I just smile and say she can call me that if she wants, as I genuinely don't mind, but months go by before she does it again ?
I am referred to as Grandma to my baby dgd, and her other grandma, who is Russian, is Baba (the most common familiar name, I think, for Russian grandmas), a name which I really like.