Driver makes decisions without account holders consent

I have been working with courier guy since the beginning and the last few months, when booking locker parcels they have been doing whatever they want. November 5 of my parcels fit in XS locker & they changed 4 of them to S and 1 to M because there was no space in the destination lockers. Today they changed it from locker to door because they are struggling with space & they just add the extra cost to my account without notifying me. Client had until 5pm today to fetch it from the locker & told them she is fetching it at 2pm, driver did not tell her it will cost more otherwise she would have told them no.

Now I want to know what gives the driver the right to change it without my consent? I am the one paying the account not the driver or courier guy. I am gatvol paying for their mistakes