SANBS - ********* behavior

I have been a blood donor for many years, Last year June I was in an accident . I received 2 pints of blood while in hospital. 1 year later I get a call from lawyers stating I Have not paid my bill and I need to urgently pay SANBS. Now to my surprise, I did not know I owed them any money. To top it all the account is just shy of R16 000.00 Now my question is, In a year, they never tried to call me, they never sent me any emails. And now suddenly just a hand me over to lawyers....... My next question is, I have been a blood donor for many years, so why is it that they are charging me almost R16 000.00 for blood after i have given them numerous pints of blood........., They never submitted the acout to the medical aid either.....