landlord and tennant case..

my landlord do the case to me.. he is saying i m not giving rent from last 3 year..

actually in realty the rent is 1200 nd in case he saying that the rent is 3500 ...we donot have any rent agreement....
this shop is from 30 year to us..we have rent slip up to 2002 ...
my father used to sit here...
last year he has died...
he is taking advantage nd saying that we hav not paid tax of 3 year
what should i do...
is there chance that court give me order to give the rent