2 ch Mini Submarines with Lights, radio Control and Charger DOES NOT FUNCTIONS

I bought three "2ch Mini Submarine with Lights, Radio Control and Charger". One is correctly functioning. The other two are not working at all. Please help me to solve this bug. I intended to offer these toys to my nephews at a family anniversary next week.

Must I send back the two not working submarines? At which address? Does Hobby King pay me for the postal transport?

Regards,
Georges Constantinescu