Collection of outstanding payment

I received a call on Thursday 29th October regarding an outstanding amount on my already cancelled account. I cancelled sometime in July 2009. In 2009 the account was settled in time of the cancellation. Since then until last week Thursday I never heard from them again. Now after - 5 years they decided that I owe them money. I asked them if there was an outstanding amount and why was I never informed. The person said that they could't get hold of me. My mobile number never changed and still staying at the same address for the last 24 years. How is that possible and I am still working for the same company since 1989. All this should reflect on their records, if they still have any record. According to me I own them nothing.<br> <br> I've been told that I never paid the cancellation fee. I also have been informed that if I pay the outstanding amount before the weekend I can get 50% discount. Today i received another sms with an outstanding amount and the amount differs from the amount given last week.<br> <br> I would like to have this issue resolved as soon as possible.