Read the forum guidelines
I have confirmed that when I turn on wireless headphones I am unable to watch Amazon Video on Samsung Smart TV. I have this Internet Package:Cox High Speed Internet Premier, DAR3402 Modem (used also for digital phone). Speed Test showed 175 mbs download and nearly 11 mbps upload. I see there is an upgrade modem available but I am not interested in paying a monthly rental fee. What solutions can you suggest?
It's not your Internet plan but your in-house network.
I'll assume your wireless headset came with a wireless transmitter to connect to your Samsung TV. Technically, that wireless connection (headset to transmitter) is a network. Meaning, your headset is communicating to the transmitter on a private channel through the air.
However, your TV is also communicating through the air to your wireless router. Moreover, other wireless devices in your household are also communicating through the air. When these wireless devices communicate through the air, they're using radio frequencies. I'm sure you've heard this before, but 2.4 GHz is a prominent frequency for consumer products.
It sounds like as soon as you power up your headset, it's glomming onto the same frequency of your wireless router. Even though your headset has a private channel to your transmitter; your transmitter, headset, wireless router and all other devices have to parse through all that chatter to decide which are addressed to what. Your network is overly congested.
Morgan is correct: either change a device to another band (5 GHz) or select a "cleaner" channel to free up your 2.4 GHz frequency. However, without getting into details...and if it's possible...and if your headset has a line-of-sight to its transmitter...I'd switch your headset and transmitter to a 5 GHz channel.
Well said, better than I could have ever explained it you should suggest it as an answer for anybody else that searches for that same problem.