bullying tactics

I was called by this firm and they told me that they are calling on behalf of ABSA, they told me I owed absa money and they have been instructed to get it from me, the person i dealt with was rude and a bully, they did not take into account my expenses and told me that I had three options and they will take a specific amount of money monthly and I told them I cant a afford that monthly installment, they didn't care threatened me with legal action, 3days later that amount was deducted from my account when my salary was paid, is this legal in terms of the NCA, can they make threats, bully me and take an amount iv specifically told them I cant afford?