Due to job loss, I got behind in my rent. I made payment arrangement with the property manager. I have his approval message that he left on my phone. Now it is 3 weeks later and a new property manager took over and has given me a pay or quit and it taking me to court for all of the back rent due immediately. She said the former property manager didn't have the authority to make the payment arrangements... yet he did anyway. I feel they should still hold up to his agreement with me whether he is still employed or not because he was acting as a representative of the company when he agreed to our repayment terms.

Landlord tenant agreements must be in writing to hold up in court. Having a saved phone message probably isn't going to help you, but you can try, since you may end up in court.
All they have to say is that the previous manager was fired and that they then sent you pay or quit notice, all legal. You really don't stand a chance.
No matter the reason (and landlords and courts hear them all), you owe rent as defined by your lease. If you can't pay rent, arranging payments is just going to put you further in debt, and you should have found a smaller cheaper place, roommates, relatives, something.