What are your working hours to be getting up at 5am? Honestly it sounds like a massive problem is your open-plan studio flat combined with your very different working hours. He is working 4pm - 11pm and understandably wants some time to unwind before going to bed but then you presumably start work very early and need to be up at 5am, understandably you therefore want to get to bed as early as possible after he gets home.
Living in a studio you are in each other’s spaces all of the time and on top of that you must be permanently tired only getting 5 hours sleep every night. That will turn things that start as minor frustrations into big ones and make it difficult to unpick what is genuinely unreasonable behaviour from reasonable, albeit annoying, behaviour. I don’t think it’s reasonable to expect your DP not to ever take a phone call when you are together but equally there are situations where it is reasonable to expect him to put down the phone. Sex is obviously one and I agree date night should be another, but things like sitting in bed together having a lie-in is a greyer area.
You can’t expect to have his undivided attention all of the time and equally if you only have one open-plan room it is harder to define and separate time you're spending together from time you’re at home together. In a larger house there might be times you're both home where you choose to be reading upstairs whilst he is watching TV downstairs and other times you would choose to do something together. But in your one-room flat you’re both always in the same room and the issue seems to be that you see time you’re both home as quality time and he sees it as downtime. Therefore he sees it as time it’s okay to take a phone call for example but you see it as an interruption.
I think it would be reasonable of you both to agree on specific times where you expect to spend time as a couple, such as date night, and to have ground rules such as no phones/ interruptions during those times. But it’s also reasonable that some of the time you are both home is free for you both to do other things like take phone calls or watch TV without needing to focus all attention on the other.
It definitely sounds like you both need to communicate more about what you want and expect because at the moment it sounds like neither of you know what the other needs and like both of you are wrongly assuming the other is on the same page in terms of what is and isn’t okay during downtime. I can completely understand for example why you’re frustrated when you’ve ignored a phonecall and then 10 minutes later he answers the phone, but equally it sounds like ignoring your call was a self-imposed rule and not something he asked you to do. You therefore need to communicate better to try and reach an agreement and compromise. Then obviously if even after you’ve had a conversation where you both outline your needs and agree on how quality time should be spent he’s still glued to his phone I think it would be time to consider if he’s worth investing in.