Hello,
I wanted to warn people about a couple of things:
1) I had Dropbox Professional with 3TB of space. I upgraded to 4TB of space. To get more than 4TB of space you have to go to Advanced which 15TB in total space but you have to buy for 3 users and you have to pay for each user. The amount is way more.
2) Once you've paid for a year (like I did) and want to cancel (since the jump from 4TB to more is prohibitive) then you would expect to get a pro-rated refund for months not used but no, you don't get any refund at all.
I would highly recommend looking for other service providers than Dropbox based on my experience with them.