enterprise rent a car vestal new york damage scam vestal, New York

I rented a car back in March and decided against taking the insurance. When i picked up the car we went out front and the fellow quickly went around car  pointing to one spot of  previous damage..I asked him 3 times about other scratches and dents and he said they were not to be worried about. he had me sign and i was off. When i returned the vehicle I had to park out back. The woman checking me in asked me to come out back to ask me about a crack under the rear fender which i never looked under the car before but walking a longer distance to view the car I then noticed it. I then argued with her that I did not do the damage and she kept asking me to sign some paper. I was so furious that I never looked under the car. I asked her where the other clerk was but he was conveniently on vacation I wrote  a letter to enterprise and a district manager called me and assured me he would investigate then I received a bill for $389.00 for damage repairs.I since have turned them into better business bureau and now i am receiving a collection company calling for payment..Im not sure what to do next is there anyone that has actually got out of this scam.I cant afford to pay this bogus repair..Im so mad..worried now my credit will be affected