Poor customer service

I had a contract with Telkom, so they didn't collect thier payment from my bank account when I ask why they told me that it's been happening to most of customers, then that was fine I managed to make that payment for those few months which I owe, now I asked them to send me a letter to confirm that I am no longer in default my account is up to date, this letter is requested by my HR for verification purposes. They are telling me that the payment is reflected on their side but I have to wait 31 days for the statement that is showing the payment. I told them that I just need a written letter to confirm my payment, they are saying they can't do that, now I am about to loose a job opportunity because of this. Kindly assist 🙏