Iphone 5 leaves black mark on charger which affects charging and syncing?

This has happened ever since i got my phone at christmas but now has become a problem. I can only use one side of the charger which is meant to be able to charge the phone no matter which way you put it in and if i move it a little it will disconnect so i have to keep it absolutely still which can't be right…
bought a second charger but the phone again left a black mark on the golden strips in the end of the charger and the problem has just repeated itself. I don't have an apple store near where i live so don't tell me to go to one as its not that easy.

The contacts in the phone may be damaged and cause a short circuit burning and damaging the charger see apple store

Email an apple store or ring up, that's not right

You're gonna get electrocuted like the Chinese lass
Quit the iPhone 5
Sell it
Tone your muscles n get sun screen

It is burning