If you stream 4K content on a 1080p TV, you will still be charged for the additional bandwidth by your Internet Service Provider (ISP) because the bandwidth is used according to the resolution of the content you are streaming, not the display capabilities of your TV. Even though a 1080p TV cannot display the full resolution of 4K content, your ISP still needs to deliver the higher bandwidth required for 4K streaming. This is because the 4K content is being delivered to your device and then downscaled to fit your 1080p TV, which means your ISP is still providing the higher bandwidth even if you're not seeing the full benefit on your screen.
It's also worth noting that the bandwidth requirements for streaming services can vary depending on the platform and the specific content you're watching. For example, some streaming services may require a higher bandwidth for 4K content, while others may offer 4K streaming at no additional charge. However, regardless of the specific service or content, streaming 4K content will always require a higher bandwidth than lower resolution content. So, if you're concerned about bandwidth usage, it's a good idea to check the bandwidth requirements for the specific streaming services and content you're using.