I bought 200GB of ICloud Storage, iCloud Settings shows 200GB, but the iCloud Storage tab says I have 4GB
Sign out of iCloud on your phone by going to Settings > iCloud > and tapping "Sign Out." Then sign back in. This will prompt your iCloud connection to update the information it is displaying. If it does not update, sign out of iCloud, restart your iPhone, and sign back in.  

Additionally, you may want to download the Ookla Speedtest app from the app store, and check the speed of your internet connection, as that is the most likely culprit of a slow backup, but will be a separate question as it involves router settings, and/or your Internet Provider.