Me and my husband have been loyal customers to Vodacom for five years, We unfortunately no longer want to be their customers due to their gross negligence

Me and my husband have been loyal customers to Vodacom for five years, We unfortunately no longer want to be their customers due to their gross negligence. They have no proper customer service and are unwilling to help loyal customers, but are very quick to cover up their own mistakes. Mistakes they made that led to unhappy customers with badly impacted credit scores due to their gross negligence. We have been pleeding for 6 months to resolve the issue at hand , but no one at Vodacom seems to care and this all due to a contract that was cancelled and payed in full in January 2025 , but was never cancelled on their side due to gross negligence. Now no one wants to help us resolve the issue they caused.