Being charged for a service not received

Earlier this year (I think May or June), I received a sim card from Mr Price mobile. It was never activated - I just received messages apologizing. Eventually I destroyed the card and continued with my current service, only to be charged on my Sheet Street account - an activation fee and a monthly fee. I have been struggling to get this cancelled and these monies reversed. Now they say I have to a courier fee?!! For something that never worked and which i no longer am interested in?? I want ALL fees reversed, but cannot even get onto their website to put my request in writing and am not interested in phoning AGAIN! I have even been in to my local Sheetstreet branch, but they could only also contact the call centre. I am at my wits end.