contact termination

i got retrenched and then later went into the shop and asked for the settlement amount and paid the amount and signed the documents for contract termination in the shop. and did not hear anything from them for a year or two. and now the lawyers are calling me for an amount and i refuse to pay it for i signed the documents to end the contract. now because someone did not file the documents or something. and now i cant take out any credit and i feel that how and why is this my problem i did everything from my side to finish the contract. this is disrupting my life and this incident was finished about 2 to 3 years ago. and now this happens.