Again,billing for the same thing more than once is not possible, as the system is set up to prevent this.
Again, why do you assume the billings are for the same subscription? Where are you seeing they are for the same thing? Just because the charges are for the same amount does not mean they are for the same thing.
Its entirely possible and more likely that the secondary charge is for something else. As I said before, Apple does not specify what a charge is for on your statement. It merely appears as "apple.com/bill" So how exactly do you know both are for iCloud?
Please follow the steps in the support document linked above, to identify the charge.
here it is again. click here ➜ If you don't recognize a charge - Apple Support