I found the early episodes awesome. It's been such a long time since I felt this way while watching a kdrama. I find the basic concept to be incredibly fun & despite the leads being a bit lacking in chemistry I felt their back and forth refreshing, interesting & even the related mysteries/thriller bits were quite well presented, for a kdrama.

Unfortunately my excitement started to seriously fade around e7-8 & by 10 I felt a tremendous amount of boredom. By e8 I thought that I had most of the plot figured out & that I pretty much know what's what with the villains & how this is going to go down.
Again unfortunately I was surprised, the script really went above and beyond my expectations in a bad way. The writers escalated the makjang to absolutely insane levels, not even a hint of sanity had been left in the show. Then comes e12 & again I thought this is it now we'll just go through the motions & we'll get some kind of a cringy super unrealistic happy ending. We've ultimately gotten that alright, but the forced separation & some of the noble idiocy explanations, the dialog related to that part is again completely insane & if we add in how she ended up "there", that's just too much.
I could talk about intelligence insulting plotholes, but I'm not motivated enough to go back & rewatch some of the earlier parts to be absolutely sure this is right.

When The Phone Rings is really hard for me to rate, because on one hand the early episodes were wonderful, but on another this drama has almost everything I hate about kdramas & Brazilian soaps. The one thing it does not have is a strong love triangle & I'm greatful for that, but good gawd all the makjang classics are present & in incredible abundance at that. Epi 11 of this show is quite possibly the craziest kdrama episode I have ever watched, we really go through all the big soap tropes and more in a super condensed way...

The OST on the whole is not great, I barely felt it most of the time, but there is an instrumental track I really liked, though it only played like 3 times throughout the entire show. It's called `In Your Arms` and it can be easily found on Youtube searching for that + When The Phone Rings.

In the final episode there are some veiled references to events that are going or went down in the Middle East, I did not watch the mistranslated version & I don't really care honestly, but it's strange the production team had to go with stuff that resembles controversial real world events, why would you step on toes like that I don't know. This did not influence my rating though, I just find it strange that this was given the okay, considering the ramifications.
Then again maybe I shouldn't be too surprised, Korean writers/directors rarely care about international success & the opinions of international viewers, Netflix or not. Just look at how often Africa comes up in kdramas & how dumb it is every single time.