In Automatic Search, you will always find all possible stations, whether programmed or not.
If you have correctly followed the procedure for assigning a channel number to a given frequency, for example, CH01 = 106.2, and if, when requesting CH01, you end up on the correct frequency 106.2, it means that the programming has been done well.
Now, to deprogram a channel, simply reprogram it to another frequency.
Example: CH01 is assigned to 106.2 and you want to set the frequency 92.4 on CH01, just follow the procedure for assigning a channel to a frequency again:
Excerpt from the manual:
Press the SOURCE button on the remote control to select TUNER, then press the GOTO key, the LCD screen will display
"__ : __" and you will enter into the "numeric entry" mode, please enter the FM frequency of the radio station you wish to listen to.
Very difficult to catch a black cat in a dark room.
Especially when it's not there...