Mobile data can be turned on while calling if you have only one sim . Try it remove one sim and you will find out that if there is only one sim then mobile data will still be turned on while you are calling. It works then you can put the another sim on another phone which you use only for calling and not for internet connection. This will increase the weight on your pocket , so you can use a keypad phone for calling purpose only. This happens in almost every smartphone😬😬😀👍👍
