I keep getting charged for storage on my old iphone, how do I get rid of the storage on the new one?

SETTINGS>>>CLICK ON YOUR NAME FOR ICLOUD>>>ICLOUD>>>MANAGE ACCOUNT STORAGE. You can select the option you want.

Be aware that the change will affect all devices signed in to your iCloud account.

Downgrade or cancel your iCloud+ plan - Apple Support

The storage charge is attached to your Apple ID, not a specific device.