Unable to return unwated upgrade

on the 17 March I upgraded with Vodacom online. They delivered it the next day. i wanted to return it and called the next week, well within the 14 day period. after 7 days there was no collection, i called again, now they wanted to tell me it was out of the 14 days and i told them they never collected it and they promised to do so, this was last Monday. and Now still nothing. When will this be collected and sorted out. I now cannot use the upgrade on something else and i am continuing to pay for it. it is more than a month now.<br> Can someone please assist!