Blatantly ignore any communication

Without my knowledge standard bank handed me over to this company. When they phoned me i tried to make an arrangement by asking for the documentation i need to fill in for them to set up a debit order. I fill in the documentation and send it back. They cant find the mail even though it is in my sent box as a reply to the mail from Busisiwe. They sent me threatening smses even after i sent them the documentation for the debit order. Then after a couple of days i asked for the details surrounding the account so i can manually transfer since they seem to receive only certain mails from me. They don't send the details, however they do send more threatening emails. I paid them and sent them proof of payment. I am trying to confirm that they have received payment and am requesting just a simple letter stating that they will not be taking legal action since an arrangement has been made. I have phoned and emailed every day for over a week. They can never transfer me to the correct people and no one responds to the message i leave at reception. Nomvula and Busisiwe are blatantly ignoring my emails and messages. For a legal company to ignore clients and then still threaten them after payment