Normally I would say use your credit card company to do the work for you. However, you've got this through Voda. Have you talked to them? You mentioned others are afflicted as well. Take it to the press, preferrably national television consumer shows. In my country there's a small courts appeal for anything under £1500. The cost of a process is limited to £50 or so, so it's a small risk. If something similar is available in your country, sue them.