Courier guy will rob you

They sent me a parcel from Durban and booked door to locker and paid for that, today I receive a call from Lilani from courier guy alberton to tell me that I needed to pay extra R800 as the parcel is above spec, what spec as I have received numerous parcels in the kiosk and never paid a cent extra, I told her to return the parcel to sender she said no but will send it to thier legal department, I told her I don't have that money to pay. If the parcel was above specs why did they send it as usually if it's over weight they don't accept it, so why bring it all the way from Durban to here only to tell me that the parcel is over spec what was that bot don't when the parcel was received from the sender as she could have done something to the parcel to meet the specs that we have never heard of.This is day light ******* or they just want to keep that parcel.