How to persuade my Step-Dad to give me my iPhone back?

So basically, on Thursday night me and my mum were arguing (like mums and daughters do). We argue very rarely because we're so close. Anyway, my step-dad decided to take my iPhone off of me and he said that I need an "attitude adjustment". I 100% get why he did it, but he wants to take it off of me for a month or so (for a 20 minute argument with my mum). I really need it back because I have anxiety and I feel that when I leave the house without my phone, i'm not safe. I don't know why? Also I need it for school and that's also the only way I can get in contact with my friends (to meet up for lunch etc.) He said that I need to really consider making it up to him for my actions, but I have no idea how to? I have no money to buy/make him anything to say sorry. I've tried everything! I told him I was sorry and that I accept my consequences but he still doesn't accept it. I didn't even do anything wrong to him, it was to my mum but he said "if it upsets your mum, it upsets me". I have apologised to my mum loads and she accepts it and she thinks I should get it back but there's nothing she can do. So what now?

Just tell him he isn't your dad so he has no rights and you'll call the police as it's theft, that will create some potential problems I'm sure he'll want to avoid.

Buy another one and hide it from them

So stupid really stupid and it sucks