Cartrack account

My account was in arrears, they sent me an email to make payment and that I qualified for a 30% discount should I make a payment. I inquired about the discount, they told me the amount I owed and minus the discount then the balance. I paid the balance and sent proof of payment to them. They called me about the remaining amount and I was so surprised because they offered a 30% discount. They were like ohh I see, you have paid. Now I received an email that they blacklisted me, for what now? On what grounds?