Do you get the notification on your computer? Anyway, be sure you are well backed up on your external, Documents, Desktop, and Pictures. Then turn off Photos syncing and iCloud Drive syncing on all your devices. Allow for/follow any messages received when you turn them off. The free amount of iCloud storage should be plenty for you to sync "standard" items like Safari bookmarks and contacts. So, I would not turn them off. Also, back your phone up on your computer now and in the future. See: https://support.apple.com/guide/iphone/back-up-iphone-iph3ecf67d29/ios