Probably the superiors did not waste time explaining the reason and just demanded their phones, then the Russian soldier stole or robbed a phone and called home

Probably the superiors did not waste time explaining the reason and just demanded their phones, then the Russian soldier stole or robbed a phone and called home since he knows there is a big chance that he will be dead soon. So if you think that your soldiers have this need to talk home maybe an competent army should offer them some alternatives, like some satellite phone they can use once a day and call home, you can't expect 18 years old forced to go to war to be professionals.