^^^this. Sorry about your continued issues. Sounds like you're at the end of your rope, as you should be, but...keep cool. Once you lose your control, you give them the advantage, and...well...just sound like an idiot. (I know this first-hand...lots of experience sounding like an idiot!
) Besides, trying to negotiate with the counter person is rarely productive, as they've got no ability to negotiate in the first place!!!
You've got the upper hand in this. Keep methodically working on them.
Good luck. Keep us posted.