The lady at randridge mall has ****** my stock

I went to randridge mall post office to post stock to two customers( I usually use douglasdale )<br> The indian lady asked me how I would be posting&I said counter to counter. She said it won't go today& I said that's fine there's no rush for these parcels. She handed me waybills & bags & I filled out the details &bagged the items. She told me I must pay R148 & I asked why it is so expensive I usually pay R30 per parcel this size. She said it is overnight and I told her I did not ask for over night I want counter to counter with the tracking no. She said that service is not offered at the post office. I told her I use it often &it is available. I asked her to change it &she refused. I asked her for my items back & she said only if I pay for the plastic bags. I told her I would &she said R148 & I said no that's ridiculous. She told me she refuses to give my parcel back as I had made a mistake. I told her I did not make the mistake &I want my stock back. She has still got my stock & refuses to give it back. I have contacted the police who will open up a case of theft if the post office has not given my stock back. How does a plastic bag cost almost 75 when it costs 30 to send.