INH Properties Trie to make me pay rent when I was not living there , Internet

I lived at an apartment called The Birchwood apartments in 2009. Before I moved out, I sent them a letter saying I was moving out. They said they never recieved it, even though I brought it directly to their office. It has been three years since I had been there and I suddenly get a collection notice saying I owe $1000.00. I paid all of my rent and on time and now I need to suffer for their mistake. They also said I damages the aprtment, but I took pictures before I moved in proving the damages were there before I moved in. They claim they are fake. I am bow depressed and I dont know what to do. Any help would be great.
Amanda MN