My parcel lost /disappeared from locker to depot

One of my parcel went missing and all they say is that the vidoe they have shows the driver taking into the depot one plastic f not two .I asked if they dont have cameras at the lockers to see how many plastics did he collect from that specific locker and noone is is giving me an an answer . I gave evidence of a video dropping the parcel in the locker .How can that be .It means only one thing their employee stole my parcel but they are not doing nothing about it .Am not a happy client at all .How can on trust such a service provider