Threats from Truworths call center agents

I am being threatened and bul**** by the Truworths call center agents number: *** and ***. I missed 1 payment when I changed bank accounts, one one agent called me I told them that my account is on debit order and it will double debit the following month. I have received almost 30 calls after that day, some of them as late as 7pm. The guys have threatened me over the phone and their response is we will keep calling you and charge on your account. They are very rude and behave like I have missed more than a months premium.