I see this conversation in Studio 21:
B: »Guten Morgen, ist dort die Firma Mayer mit A-Y?«
A: »Nein, hier ist Heier. HEIER.«
B: »Oh, Entschuldigung ...«
What is the ‘mit A-Y’?
In ancient times, a Meier was a land agent (the administrator of an estate). The estate that he administrated was called Meierei.
Today many people have the name of this old profession as their family name. But there are dozens of different spellings with exactly the same pronunciation [ˈmaɪ̯ɐ].
Some of the most common spellings are:
You often say some similiar explanations to clarify the spelling for family names with a spelling, that is not so clear when you just hear it. For example, I often say:
»Schölnast (nur ein L, das L vor dem N)«.
It's simply spelling out a and y for clarification.
That's done often with last names like Mayer, because there are many other common spellings of that name like e.g. Meier or Maier.