Harassment

I have been getting numerous sms messages from this company claiming that I owe them R500 in short paid fees that is owed to the Sefako Makgahato Health Sciences University. I left the university in 2017 and all of my fees were settled in full. When I called them a few weeks ago they said that they would find out what the issue was but they have not yet resolved it as I am still getting messages saying that they are handing it over to their legal team if I do not pay. I refuse to pay them as this is ***** and a huge ****.