ADMIN FEE 2 YEARS LATER

I have received an SMS advising that there is an account outstanding of R358 which was an admin fee, with the threat of legal action if the account is not settled by 11/1/2020. I have no idea what this is for and tried contacting them on the number provided which was never answered. I eventually contacted casualties at the Glynwood Hospital. I was then informed that their accounts were hacked and the amount outstanding was from May 2018. This was paid on admission. I find this extremely unprofessional. They have my number and could have called. How can anyone be held liable for an account that is over 2 years old.