Is it possible to owe a bank more than 6000 which is not a loan

I was banking with standard bank while I was at school, I haven't use my standard bank account more than 3 years now. This year the lawyers are calling me everyday to make arrangements with me on how am I going to pay the more that 6000 Rands I don't know how I end up owning them, please help I donr know shat to do, I tried to find out whay and how but no one give me a clear answer