What does a lawyer do when disputing a matter on the phone?
STEP ONE OF THREE
Have a piece of paper and pen handy, not your bill, invoice or whatever you are disputing. Keep that document clean because it may be evidence later. Don't take notes on your device, those are terrible for storing evidence--they get lost, broken, and autocorrect important words you may forget later.
If you can put your phone on speaker while talking, it may be a good idea so that you can write down notes, so make sure you are in a quiet and private place.
Write down the correct spelling of every name of every person you speak with on the phone, the time you spoke to them, their direct phone number, and a brief line about what you said--this is true even if they send you to someone else.
Hold them all accountable. They may be recording and storing your call. Later on, having the names and times will make it easier to find the recording.
To recap, step one is to write down everything.
Your lawyer will want this later if it goes that far.