three sets of headphones not plugging into brand new lg optimus g phone
Take it to the shop you bought it and get them to work out what's going wrong. This isn't the sort of problem you can easily fix over the internet: you need an expert there to see what's up with the jack. In addition, if it's a common problem, the people at the shop will already have heard about it from other customers. Maybe the jack is just too tight and needs some more force, or maybe there's some fluff stuck inside where you can't see.