I'm sorry to hear about this. I'm going to ask several questions to help clarify what's going on here: what's the complete model code of the TV? Does this happen on all DVDs, Blu-rays, and video streaming apps? Does the Blu-ray player get routed through a home theater of any kind?
I have a series 6 3D LED Samsung TV and a BD-F5900 Samsung Blu-ray player. These are connected by an HDMI cable directly from the blu ray to the tv. I can start a movie and the audio will be very close to the correct sync, but about an hour or so in, the audio sync starts to get worse and worse. I have updated the Blu-ray firmware and there is no improvement. Any help on what I can do to fix this issue? I would think that samsung blu ray players and samsung tvs would work well together since the same company makes both of them.