Account was paid and closed

I have an account with Telkom for sim card contract and it ended on 02/07/2021 and was paid in full and after the contract ended, I received Aa statement that say I owed R301, and I tried to find out via Facebook and the consultant called Maggie confirms that account paid and closed. Now recently I was applying for a loan at African bank and the application declined because of AB LEGAL COLLECTION/IN ARREARS.