Switching from $10 to $5 nitro while keeping original subscribed date

As the title states, I wanted to switch from the $10 nitro version to the $5 version in order to save some money. I've had the base nitro since 2018 and updated to the $10 version originally for the little game shop that discord had awhile back. Unfortunately, that was taken away and replaced by boosts. I decided to just stay subbed and just boost my favorite servers at the time. However, I am needing to save a little bit of money now in my life and I wanted to downgrade from the $10 version of nitro to the $5 version while keeping my original subscribed date which was back in 2018. I was told that my date would be reset once it switches. I feel like there there should be a way for OG's in my situation to be able to downgrade or upgrade their subscription without losing that beautiful originally subscribed date. The option to switch between the two already exists but it should not reset your original subscribed date if you are still subbed in some way.