👍👍👍👍 Before asking a question, you are generally supposed to know something, (and essentially the basics) about the topic on which the question is asked...
Thanks for being with Samsung and sharing your concern. We would like to inform you that once you have selected the auto mode in 1 slot then you need to change the network mode when you will switch to another slot for selecting mobile data. It is default feature of the device can not be changed.