Dropbox is stealing my space

I had an account using DropBox Pro. I have changed job and do not need this anymore, but want to keep what I have and use it. I have earned in total 10.25 GB, by inviting various friends to use DropBox. I am using 8.2 GB today - there should be plenty of space left for a basic account, correct? But downgrading to DropBox Basic leave me with only 7 GB and a useless account. DropBox amswer: "when you upgrade or downgrade, the extra space you got via making referrals will be worth different values, depending on your plan. So it does look like you will have 7 GB as storage space".

The result is that I am loosing 3.25 GB = DropBox is stealing my rightful earned space and remains with a useless account.

Rich