University of zululand

I completed my degree in 2006 and graduated in 2009 because i was owing the university, so i had to pay the debt before i graduate. So now my problem is in 2019 i received a message saying i am owing the university of zululand, and i was very shocked because i don't understand how did i receive my degree if i qas owing them and why after 10 yrs, so i need answes coz this is really annoying and now they are threatning to send summons. Iam very dissappointed, university of zululand, you are conning me.