SPCA - OUTSTANDING AMOUNT

i keep on getting sms's and emails w.r.t a bill from the SPCA from 2011. nobody, from 2011 up to end of 2017, tried to contact me w.r.t this outstanding amount that I owe. Now all of a sudden they could get hold of me to claim I owe them money. As far as I know this has become Prescribed debt after 3 years. Please stop sending me messages or emails w.r.t the outstanding amount.