[Q] Charge port picky on charging

So my wife has the S3 phone, and when she plugs it in, she has to do a song and dance just to get it to charge. While it's just sitting, most times the connection notification sound will go haywire as the connection is loose. I've tried using different cables and it's the same thing. It's a factory phone, no mods done to it as she'll kill me if I do anything to it. Has anyone dealt with this? Did you bring it in? Would I be charged a fee to get it replaced with the same phone? Thanks for your input.