Test one thing at a time. It feels slower and it is the only way to learn anything.

Written confirmation email after every phone call. Cheapest insurance there is. Eight months in on a travel letter and it lines up.

Sorry for the basic question, but how do you actually start one of these diaries?

This is the correct amount of effort for a thread like this. Same for me with a thing you bought, unfortunately.

Bring a list. Embarrassment makes everyone forget things, including you.