iPhone 4S charging problem

Hi Guys!

I have recently discovered charging problem with two year old 4S.
When I plug it with charging cable it starts and stops charging right
away. You have to place it in a specific angle so that it charges. So
you can't really use it because it will stop charging as soon you pick
it up.

Is there a fix for this or should I start looking for a new phone?

Thanks for the help in advance.