Making a deal on the phone? Can I sell you some property in FL on the phone? :-)
Not to insult the OP, but Lauren is absolutely correct. NEVER tip your hand about ANYTHING prior to speaking in person. There's too many unknowns. Get everything in writing. And NEVER tell a salesperson how much per month you are willing to pay. They will make the numbers come out to what you want but you most likely will get hosed. You can increase your credit rating by reducing your debt, cancelling credit cards (in writing) if you have multiple cards and by decreasing your card's credit limits (in writing). That said, call around or go to other dealer's websites and see if they have the same trailer and go talk. Shopping around usually pays off. And you are correct, their treatment of you was very unprofessional.