So why exactly is this my problem?

The phone just rang. Jakob (strapped to me in his Baby Bjorn) and I got to it moments after the machine picked up. Someone calling to remind me about the appointment for his immunisation tomorrow.

Huh?

I tried reasoning with the woman on the other end of the line.

Me: "He had his 6-month shots on March 29."
Her: "So call Marilyn and cancel."
Me: "No, what I'm saying is he has had all his shots. There never was an appointment for tomorrow. I don't have an appointment to cancel because I never made an appointment."
Her: "I'm just the switchboard operator. Call Marilyn yourself and cancel."
Me: "I don't even know who Marilyn is! I also don't have a free hand to get a pen and paper. If you're in the same building as her, why can't you tell her?"

That's when I realised she'd hung up on me.

Why am I responsible for cancelling an appointment I never made?

Yeah, I'll just add that to my never-shrinking To-Do list.