Rewards Promotion - not applied

Recently in Oct month purchased an iPhone 15 pro max since I got $830 off from rewards as a gold member. It was applied correctly in the first-month cycle bill. in the following month, the promotion credit was reduced and I crossed over the return option.  I got frustrated with several hours of spending phone and each time customer service will say it's applied now and never reflected in the bill. Finally went to the store and opened the case (ECM0005165216). The case has been open for a long time and went to the again store to check. They told me that the case would close by 10 am of last Friday. but still not closed and no help getting over the phone. They simply disconnect or transfer to someone. Worst customer service over the phone. Store people are knowledgeable. Another interesting factor was I was cheated by sales folks that I would get one free mobile line(12 months) for every two lines you added. Any help is appreciated.