If you bought the phone from MPD then the buck stops with them. This is standard UK Sale of Goods Act. It is unfortunately quite common for retail staff not to understand their legal obligations. The device should be sorted by the point of sale not the manufacturer. In the past I have found quoting the relevant section of the Sale of Goods Act helps and very occasioanlly a threat of court action is required. If you want some backup then the local trading standards office (see yello pages etc) should be able to help and maybe even intervene on your behalf.