Snapped at for sealing Paxi bag

I went to deliver a parcel at Pep Elliot via Paxi, I bought a bag and was told I'd be assisted by another cashier with sending the parcel... I packaged it into the paxi bag while I waited for the cashier... she came snapping at me for sealing the bag and told me she had to strip my parcel first before I inserted it.

My problem is that i paid for this bag and THEN i was told my parcel had to be stripped. Is this the process that you follow with all your clients or just those you have no respect for?