Sensitive screen after LCD screen replaced?
When making calls the phone will go on speaker or mute after the LCD screen was replace
第四代iPhone。维修过程直观易懂，但前置玻璃和LCD面板无法分开，只能作为同一零件更换。GSM版本， 8, 16, or 32 GB 容量 / 型号 A1332 / 黑色或白色
This actually sounds like the devices proximity sensor isn't functioning properly.
If the screen were "too sensitive" then the issue would also be present when the device is away from your face, such as the reported ghost fingers issue.
Chances are the device requires a UV screen over the proximity sensor. Some devices, such as the white iPhone 4, must alway have this or the result will be exactly as you've stated.
If you need parts for your fix, I'm sure you can get them here at www.ifixit.com