SOS Protec annoying previous customer

I complained about the SOS Protec i think in Feb 2021, i was previously their customer and terminated the contract with them and i even sent them my email to proof that i communicated via emai as they claimed that they didn't receive any email. During Feb 2021 i resend the email and afterwards tbey did not come back to me as they were pestering me about the outstanding amount of which i don't owe. So today 24 May 2021 i received an sms as per below: Immediate Pmt required SOS Potec Sure acc by 28 May 21@12H00. Due R524.94. Saya 0117675300 WhatsApp 0810080109. Ref 102692377

I really don't know what game are they hoping to play here. As a matter of fact i will print all the mails and go to SAPS to report this company if they continue to irritate me with this stupid sms. Regards