How to check return postage charges

Good evening,

Is there a way I can double check that the cost of the return postage has not been charged to me? I have received a return which was an ‘accidental order’. When I authorised the return I chose the option Label Type: No Label (which I assume means the customer has to purchase the return cost). The reason I am asking if there is a way to check is because the returned box has 3 labels on it. 1 label, which is the standard post office 1st class small parcel stamp and the other 2 are printed labels which I assume have been printed from the order details (they have the dotted outline which sometimes denotes it is a label on a pre-paid sheet). I just want to check these have not come from a pre-paid label print off.

Thank you kindly