I have more storage than it shows why does it make me have low storage

If you purchased more storage, you didn't buy it for your iPhone. Once purchased, the storage on an iPhone is fixed and can NEVER be enlarged. You can however, buy more space in iCloud, which permits you to sync more data with iCloud. Chances are you didn't need to buy more space in the cloud and I suspect you were under the wrong impression that buying the storage made more space on your phone. It doesn't, because it simply can't.

Read this link about the difference between device storage and iCloud storage --> What's the difference between device storage and iCloud storage? - Apple Support

You have 2TB of cloud storage. That is not the same as the internal storage on your phone. you can not increase the local storage on an iPhone.

There aren't any iPhone 12 units with 2TB of internal storage; iCloud space is separate from that inside the device.

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