
I'm not blaming the seme. But I would have tried again or texted instead if he hung up. Don't know about Korea but where I live it's more and more common for younger people to not pick up Unkown numbers and instead text their friends on apps to let them know that it's them if they've changed their phone number etc or are trying to reconnect.
I think the author didn't think this through.
The Uke seems to have anxiety, if I were the partner and I promised something like that I would have tried otherwise it shows a lack of effort.

relax girl ,, well basically when he didnt answer it the seme , hurriedly done everything need to be do e to get back home early ... you know, their relationship isnt out yet , thats why he only try to call him using different phone , not text him maybe because he knows ... well thats why I think it. also i would be like the uke too ,, i know how it feels ...
spoiler , that i think everyone knows ..
he phone was broken so, yeah that happens