Vodacom refuses to close my account

Still struggling with the closure of my account. Months after paying in full it still appears as an open account on Experian even though Vodacom says they’ve closed it. I’ve been calling and sending emails since February and I get sent from pillar to post with no one knowing exactly how to help as that number has been given to someone else. This is affecting my credit score, I’ve tried getting a paid up letter from them to send to Experian so they can update my details but no avail. Incredibly frustrated and disappointed