Bought two USPS shipping labels- how to get refund?

[BRBHMA]

I bought two shipping labels for the same box- on accident.

I "voided" the first purchase, but I don't see anywhere that it will let me get a refund.

How do I request a refund?

I am mad about this- when buying directly on USPS, there is less room for mistake and it is easy to get a refund. 

[Whac-A-Mole]

you wil get your refund once USPS determines you have not used the label,usually x number of days