"I think your being unreasonable in your expectation of a reply so quickly tbh"
One single sentence that sums up in so many ways the p.poor attitude to customer service by big corporates, which is inculcated into their staff.
I have run several successful customer focussed businesses, and I would be really concerned if it took more than a few minutes to make a meaningful first response to a customer complaint. I would be terrified to think that I had a customer focussed business which was running a several day backlog just to get out a meaningless acknowledgement letter. What does that say about the number of complaints in the system ?
Personally, these days, I give big corporates 7 days for a meaningful response, and if not, they get 7 days notice followed up by a summons (it's easy on-line). That seems to be the only effective way to get things done in a satisfactory time-frame.