Overcharged

I was quoted R380 over the phone by PostNet Parys but charged R590 when I handed it in. No one seemed to know what exact price to charge so I paid it. When the parcel arrived in Margate, I asked the Margate branch to quote me on the same parcel. The quote was R350. I have taken it up with the Parys branch and they are refusing to refund me the money I was overcharged. They do not even have the decency to respond to my e-mails. I want to make it PERFECTLY clear I DID NOT ASK FOR OVERNIGHT SERVICE!!! I have spent over R3200 in the last month and a half at Postnet Parys. I will NOT recommend ANY POSTNET to my customers in future.