It seems Leeteuk had his phone number leaked.
Super Junior's leader wrote on his Instagram, "Everything's fine, but please stop calling or messaging in the middle of the night. I think my number has been leaked overseas. I have to go record early in the morning. Please have pity on me and call me in the afternoon instead. Please.."
He'd had a similar issue back in 2012, so hopefully these 'fans' stop waking him up in the middle of the night.