I have had luck in the past; keep trying!
FICO 9: 
Filed Chapter 13 on 6/1/2017 after job loss. Discharged 6/1/2022.
Goal: Gardening!
Filed Chapter 13 on 6/1/2017 after job loss. Discharged 6/1/2022.
Goal: Gardening!
They are real, but they are the exception to the rule. And I would say that getting an immediate positive response is the exception to the exception to the rule. You're almost always going to get denied at first and several times thereafter. The people that have the most luck with GW requests are those that are the most persistent.
Remember, you are asking them for a favor. Don't write them a letter complaining of poor customer service because they are continuing to report accurate information. That's not poor customer service. Even if your comments are limited to it being poor customer service because you got a canned response that seems like they didn't read your letter, still that's not going to help your case. You need to remember you are asking them to do something that is outside their normal policy.
Also, if you started with a GW letter you found on here or elsewhere on the internet and changed a couple details in the middle to fit your situation, I would just throw the whole thing out. Start over and write a letter without looking at a template. So many of them start off the exact same, something along the lines of:
I am writing regarding my [lender] account and to respectfully request a revision to some late payment notations listed on my credit reports. Your customer service representative suggested that I write to you for a "goodwill adjustment." ...
I've seen a lot of letters floating around out there that start off like that. That means that the person who received the letter has to have seen countless ones like it. It's clearly copied somewhere from the internet. It doesn't sound genuine. There's probably no chance any customer service rep told anyone to write in asking for a goddwill adjustment. So right off the bat the reader isn't inclined to engage with you and help you. They just toss it aside as another person who copied something from the internet thinking they can get their credit reports altered.
This might all be irrelevant to your situation, but when I wrote my first GW letters I made that mistake. There's no magic language you have to use. You're basically just asking them for a favor. You're much better off putting the template aside and trying to write the letter based only on your experience. And keep trying.
Starting Score: ~500 (12/01/2008)
I got HSBC to give me GW adjustments for a 90 day late and a 30 day late, so they do happen if you are persistent enough. I was rejected several times and even was rejected after going through their executive office over the phone, but they eventually did it. Just keep trying and it will happen.
