If you want to turn off the IR permanently, you need to ensure the threshold to turn on the infrared will NEVER be reached.
First, you need to go to the OSD menu of the camera by using preset 95 + call.
Here is a video that tells you how to do that:
Now please make sure in the IR Setting, the following relationship is met:
IR ON SENS > CURRENT LEVEL （at night time）. You can set the IR ON SENS to its maximum, which is 254.
For 507-20XB, if your camera is purchased after 1.1.2017, it is likely that the maximum value has been changed to 250. The CURRENT LEVEL range will be changed correspondingly.
If you are using 507-20XB, then preset 120 + call will display the CURRENT LEVEL and preset 121 + call will remove the display.
Here is a picture for your reference when the infrared is completely OFF for 601-D20X:
But if your CURRENT LEVEL is at maximum (254 or 250 for 507-20XB), this means your ambient environment is completely dark and the IR will be forced on.