FNB no adherence to business SLAs communicated with clients

On the 12th of December I received the following email from ***

“Good day MISS XX

Thank you for your request.

Please note credit card account has been closed and the closure confirmation letter will be sent within 24 hours.

Regards FNB Card”

I called in when 48hrs passed, enquiring about the conformation letter of closed account and I was told that it would be escalated. It’s 6 days later, and I have not received the letter.

Who else can address about this level of disservice and lack of adhering to their own SLA communicated with client???