Poor service

I requested my account to be canceled on the 2nd April. Consultant advised of the 20 days notice period which I had no issue about. Then I started getting annoying calls and whatsapp that I still owe R157 while you debited R121.24 on the 6th april which I was told is prorata. I even received a confirmation letter that the contract is canceled. So if you saying that I owe you, why did you debit a lesser amount? Can you please stop calling me daily as I will not pay you any extra amount.