Vodacom Billing Department the most *********** bunch of ****holes

Today 16/10/2020 I received an email from Vodacom Subscriber Collections with a final demand letter dated 30/09/2020 requesting an outstanding amount on my account. My Vodacom account was settled in January 2020 because I have immigrated. I also closed my South African bank account since then. When I settled my Vodacom account in January 2020 I asked for a settlement statement and made payment in accordance with the settlement statement. I would like to understand why Vodacom is sending me a letter of demand if my account was settled. Why I am receiving this after 9 months since settling my account? I believe Vodacom's accounts department is the most *********** team in South Africa. I regret dealing with Vodacom in the first place. I have been a loyal customer since 2008 and I have never missed a payment. The only reason I am paying this final demand is because I would not like to have my details handed over to a credit bureau. Such a shame that Vodacom's account department's incompetency is leaving a bad taste in many individual's mouth.