Well if you have a letter from them confirming that they received your notice to vacate and understand the date at which you're doing it, just take a copy of it down to them, show the head bitch in charge, and it's a done deal. I'm assuming the letter you received from them is signed by someone in charge there, correct? If so, pay what you're responsible for and leave, if they try and come after you for an additional 5 days of rent it'll suck in court for them if you have that letter.