TOO HOT TO HANDLE no response

I sent an e-mail to FNB card division as well as CSR on 6 January regarding interest charged on my credit card statement on 30 December 2020. I only got one response on the same day 6 January, confirming receipt of my e-mail and that they are attending to my request REf ***. It is now 17 January and I have had no feedback. Do you have so many problems that you can not respond to a customer in 10 days!!!