Pretty sure she doesn't have a way to call him.
The club manager&owner takes away all the employees phones.
The employees have to ask permission from one of them or the bodyguards by the atm for their phone to use.
You really think grandma could call the number back and just ask "yes, hello? I'm calling to speak to my grandson Taeju."
I mean, maybe she COULD, but fat chance in hell that the message will reach Taeju.
What I don't understand is why Taeju didn't call Grandma earlier to tell her his coverstory
" Hi grandma. I miss you! I'm working in a factory with terrible phone reception.
I'll try to call when I can!
Please, I'm working to clear the debt and go back home, so keep yourself safe and don't lose the apartment!"
Like... you're telling me you're worried of a thug debt collector hurting her , but you don't call to keep in touch & communicate anything???
So all this time your grandma thought something had happened to you, you haven't come home in a while, she's heard nothing from or about you UNTIL THAT DAMN PHISHING CALL!?
How the hell she getting scammed call your grandson first your fucking up his plan to get u and him out of debt like dont waste his time he dont wanna sell his body