A couple of days ago, I had this conversation with a client:
Client: Did you want to have a call?
Me: Yes, I'm available on Monday morning (9-12).
Client: Let's do it at 10.
Now, even though we talked about having this meeting, I haven't received a calendar invitation, as it is usual that he schedules the meetings and sends the invitations. Today in the morning, I arranged a meeting with another client for the same time. I only remembered the conversation with the first client just minutes before I joined the (new) call, and since I didn't see the slot in the calendar I just had the call with the second client.
How should I handle this? Is it rude to say 'hey I'm in something else', we didn't schedule anything? Or you can't cancel a meeting that wasn't scheduled?