IPhone 4S charger has melted?

Okay so i have had my iPhone since october 2013 so it hasn't even been a year & between that time, i have bought a total of 6 chargers! At the end of the day, they either stop working unless i holddm phone in a certain position, or they start saying "the charger is not compatible with my device" my recent kn just melted. This is the first time it has happened. There's no problem with the adaptor but the usb part where i connect to the adaptor, just melted off for no reason! I can't call APPLE CARE because they keep telling me to pay to speak to a customer rep. So why do i do now? I really don't want to waste my money on a new charger for it to repeatedly get spoilt!

Plug? Electricity?