Words have meaning. Grammar has a purpose. The joke-teller is necessarily within the store making a call to an unspecified “her” for unspecified reasons and we know this via the rare skill known as reading. Just because a vocal plurality of people interpret a Rorschach inkblot test or a Jackson Pollock painting as a specific message, that does not make those pieces mean anything, let alone any specific one thing or analogous things.
The joke is so poorly phrased that you inverted the roles of who is shopping
Because the joke doesn’t change depending on who is in the store.
It is the exact same joke.
“call” is a transitive verb.
“from” is a preposition.
Words have meaning. Grammar has a purpose. The joke-teller is necessarily within the store making a call to an unspecified “her” for unspecified reasons and we know this via the rare skill known as reading. Just because a vocal plurality of people interpret a Rorschach inkblot test or a Jackson Pollock painting as a specific message, that does not make those pieces mean anything, let alone any specific one thing or analogous things.