Unknown debt.

I received an sms from a strange number advising me to pay or i will be handed over. I am not sure how the people received my personal info as no consent was received from me. i sent an email which was ignored. When I called they advised they work with hospitals. I was hospitalized over two years ago and if there were outstanding amounts. The least the hospital could do is to call me themselves, write a letter and email or post. i have been calling their number to no avail. I am not at all impressed with them. Do they not have an accounts department?