I have a Galaxy S9+ smartphone and am basically homebound, so use cable broadband which includes 300GB per month. Past two months, Samsung Cloud has used up almost all 300GB to the point where there's not enough data left for me to stream Netflix or Hulu I pay for each month. First tech I spoke with said he'd fixed it through Smart Tutor, but clearly not, then last night I texted with another tech who disabled Sync, as the phone won't allow me to get rid of Cloud or disable app permissions for calendar, contacts, etc. After he did that though my email app wasn't downloading emails as soon as they're sent, so I had to resync the email app. Don't know if it's related, but shortly thereafter, my Facebook was hacked, sending a video to my Facebook friends I didn't send, so I reported it to Facebook and changed my password. Being that there's 3 days left in November, I keep checking my broadband data usage to see if it keeps going up. I also sent an email to Samsung's corporate office, as I can't afford to pay an extra $25 a month to my cable company for unlimited broadband, as I live on a low fixed income, but regardless, Samsung has no right to upload from our phones to Samsung Cloud without our permission and deny us a way to disable it. The tech said the only way to disable it is to delete my Samsung acct, but then the phone won't work at all. What a racket!
We can open the Samsung cloud app and on the main page select gallery. Once the gallery sync interface is open turn off Sync. Back to the main apps page and select the the 3 vertical dots in the upper right hand corner and select settings. Once that opens select Sync and Auto Backup Settings. The page that opens is on the sync tab you can turn off Sync for each app on the list. The tab next to it is the auto backup settings and we can turn off every item on the list.
Samsung Cloud will no longer be uploading data to Samsung cloud.
The gallery sync option is probably using the most data followed by the auto backup option. The apps syncing, messages, calendar, notes etc don't use much data at all. I use other synced data to select which ones I want to auto sync.