Available options for a cloud storage upgrade would include 15GB, 25GB, and the 55GB storage plans per iCloud account.
Here’s how to upgrade iCloud storage on iPhone 4S 16GB model:
1. Tap the Settings icon from the Home Screen. It will lead you to the Settings menu.
2. From the Settings menu, tap iCloud to continue. You will then see the iCloud settings menu.
3. Locate and tap on Storage & Backup. The iCloud Storage & Backup menu will appear.
4. Locate and tap on Change Storage Plan for you to change your cloud storage. You will then be prompted with the Buy More Storage screen, where you can see your current plan, as well as the available upgrades for you to choose from.
5. Tap on the upgrade plan you wanted to have and tap the Buy button to continue with the purchase.
6. If you will see a screen asking for Apple ID password on your Apple ID account, enter the correct password and tap the OK button.
7. You will see the Upgrade Complete message, confirming your new iCloud storage capacity/plan. Tap on OK to proceed to the iCloud Storage & Backup screen.
8. Locate and tap on the Manage Storage option for you to see how the allocated online storage space is being utilized.
9. From the Manage Storage screen, tap the name of your account to see more details for a specific backup. (You may see a list of several backups, especially if multiple iOS devices are linked to your Apple ID account.)
You will then see more cloud storage details on your iPhone 4S 16GB including the latest backup, backup size and the like. Once you are seeing this screen, it means that your iPhone storage has already been upgraded. You may purchase additional iCloud capacity at any time. Nevertheless, it is always recommended for you to consult with your carrier first, regarding your service plan and current rates.