Hmm, that's really weird >.< I have no idea what would cause them to not work for you both the calls and CGs :( I can't even think of anything much to suggest other than me sending you a dev build and then getting you to send me any error logs that your PC throws up.
There's one thing I can think of to try, but it's a long shot. There's a bug that happens if you're using the skip function during the scene where Acheros is introducing Nine to Kiol. If skip is active when Acheros leaves, it can break the save/load function of the game. Maybe it breaks other stuff too?
Cos I have no idea why using skip in that scene breaks the saves. And I know using skip in other points of the game can cause weird, less serious little bugs, like voice lines repeating, BGM overlapping, and stuff like that. So if you haven't already tried it, you could try and start from the beginning without touching the skip button at all until you get to the point where you can access the phone, and then see if it somehow works.
I'm guessing it's probably not the skip function that would've caused the issues you're experiencing with the calls though. The fact that you can't unlock some CGs as well makes it even more confusing since the phone for making calls and the CG gallery aren't related >.<
I wish I could just magically transport your PC to my house so I could run tests easier x3 And I'm also guessing that if you're having problems with the phone + CG gallery, there are probably other bugs for you as well in different places that you might not have run into yet cos something's not right :(
With the phone, does it let you click the buttons and do you hear any SFX when you click them if it does let you? Or does it not let you click the buttons in the first place? Also, do all the phone buttons have numbers on? Or are they blank?
I'm just trying to figure out whether the UI is even loading for the phone or if something is preventing it from loading up.
And this one is gonna sound really crazy, but I guess I might as well mention it just in case since a lot of people play VNs with the sound muted x3 but do you have the SFX and voice volume turned up? Because none of the calls you make have text like the normal parts of the game do, so the only way you can experience them is by actually listening to them. I think I also made all calls only go in 1 ear, so if you are using headphones/earphones, the sound will only come out of 1 ear during calls. And if you're using like a left and right speaker, I guess it will only come out of 1 speaker. It was the way my brother plays games that made me think of that cos he plays with headphones, but he always has 1 ear on and 1 ear off cos he doesn't like having both ears covered, haha. Actually, the text box does come back in calls if Nine has something to say during the call since Nine doesn't have a voice, but during calls where Nine doesn't speak at all, there should be no text whatsoever, just sound.
Sorry I'm not much help anyhow >.< It's super hard to try and get to the bottom of what causes bugs on other people's PCs if everything's working okay on mine :( It's so frustrating cos it's like, as a solo dev, I'm basically stuck when people run into problems T_T
I don't mind creating and sending a dev build to you if you wanted to boot it up and try and send me your error logs. I won't know how to read the error logs/make sense of what they say though cos I'm not a coder. So I'd have to ask on the software's help section of Discord or something to see if someone with more knowledge could help me decipher them and understand what's happening.