Employee Incompetence or Bad Management re Accounting Error/s

I've been a loyal customer with Vodacom since they started business in South Africa. It's been an "uphill-downhill" experience at some stages over the more than 30 years I've had a contract with Vodacom. In all this time, Vodacom has NEVER (even though I am a pensioner who does NOT receive a monthly pension) bothered to reach out and offer me a "special deal" as a "thank you" gesture for continued loyalty. However, this past month - as has happened on a few occasions in the past - I received a notification that my Vodacom account is in arrears. Payment of the relevant account was made in TWO (2) payments to Vodacom with obviously the single same account reference for the particular account, AND the amount owed. Despite this, Vodacom persists in contacting me claiming that the account is in arrears?!?!? I am unsure of the competence of the people employed at Vodacom's accounts department, however, I cannot for a moment, begin to think that Vodacom would employ "***********" people without any experience and qualifications to work in such an important environment. Can someone in a senior position at Vodacom please attend to this unresolved issue as a matter of urgency, and rectify this situation without any further delay. O, and please confirm with the customer that the matter is resolved.