Constant harassment

This company continues to harass me via phonecalls, emails and sms. I pay when i get my salary. Truworths will acknowledge my payment then soon after i wil get an email or sms from blake and associates threatenimg me to make payment and that i have not paid. This is ridiculous! My account ws r11000 + now its just over r2000. So obviously i have mad a big dent in the amount owing and i continue to pay. Are these emails and calls and messages just a ploy to add to my bill? I get emails in july 2021 to say that an arrangement can be made only by april 2021. How dumb are these people? Im fed up of their harassment. I am clearly paying my account. Go bother someone else!