Maladministration and very poor service.

I was contacted last year September and was requested to make payments. I asked for balances and an arrangement was made to settle the balance. I did make successful payments as per the agreement to settle the account. A month later I requested for a paid up letter and was told I still owe. Now I'm receiving threatening sms's requesting for payment. It doesn't help calling the number as the people who answer are straight unprofessional and poor at giving service. I'm now told my account is sent to administration. That's straight ******** me. I paid what I was told I owe and now I have to fight for BS because of their maladministration