Sena 10U faulty unit

Shortly after I started using a Sena 10U Bluetooth headset the left earpiece started crackling at moderate to higher volume. Although it wasn't ideal I decided to turn the volume down to just lower than the crackling volume. A month went by and then while on a ride with friends the unit switched off all together and wouldn't switch back on. Although was fully charged the night before I charged it when I got home (till led on both headset and remote was blue) but no matter what I tried it wouldn't switch back on. I left the unit for another two days hoping whatever is causing the problem might \resolve itself"in the unused time but by the Tuesday morning there was no change. I contacted bike2bike and was told by Gillian Price that I should return the unit at my own cost and that they would reimburse me for the postage if the unit was found to be faulty. I send it off (included insurance) hoping they'd find the fault but they reported back that it is working as it should. I'm 100% sure that the unit is indeed faulty but because they can't replicate the above mentioned issues i now have to pay for the postage. No working (charged) electronic unit switches off and won't turn back on!!"""