Hi @Yee Man Chun ,

As I shared comments in code you need to give the correct backend choice value of On hold reason field.

To check the values right click on the field and configure open the dictionary.

Refer below screenshots.

You need to provide your choice value in above you can see for Awaiting Caller value is 1.

if you provide correct value for On hold reason it will update.

Once it is automated why you need to select manually.