Vanderbilt Mortgage typed contract mistakes Maryville Tennessee

my wife and i entered into a contract in october 2001.  assumed a loan from vanderbilt mortgage.  in the payment area in called for 240 payments of 259.00  the next clause was one final payment of 193.00 in february 2012.  made that payment and vanderbilt said that the contract wasn't paid in full at that time and we had to continue to make payments until 2021.  we walked away from the mobilehome.  so if the contract says one final payment in 2012 that should mean its paid in full or its a null and void contract.  person working at vanderbilt acknowleged that thats what the contract said.  this is really a rip off.