Cancelled account handed over to MBD (after 10 years of debit orders)

I am lodging an urgent dispute regarding a Letter of Demand received from MBD Attorneys for an allegedly outstanding balance on my cancelled Vodacom data account. This account was formally and successfully cancelled in October/November 2025. Prior to this, I was an exemplary Vodacom customer for over 10 years with an unblemished payment history and zero defaults, managed via automated debit order. Vodacom has ********ly transferred my personal information to a third-party debt collection agency without any prior communication. No notification of an outstanding balance was ever sent to my primary contact details or email before this escalation. This is a severe internal administrative oversight following my cancellation. I will not be held liable for any collection fees, legal fees, interest, or the alleged principal debt for a simple amount of R300. The worst part is these are the kind of things that affect your credit profile and after receiving the email I reported it as *****!