iphone earbuds's right audio channels gives no output
My iphone earbuds' right channel isn't giving any audio output. Earbuds from a third party manufacturer gives output on both channels.
I have checked "Accessiblity" settings and the "Mono" mode is off. Is there anything else that I might be missing? Or do I need to make a visit to Apple store for replacement?
iPhone 4S, iOS 6.0.1