ANSWER - To be honest, the most likely way of getting your phone back is being upfront about what you have done wrong, apologising to your mother and asking her to give you your phone back. I realise that may not be the magically inclined advice you were hoping for but sometimes the simplest ways are the best. Why use a sledgehammer to crack a nut etc…
However I will give you a heads up on manipulation magic as I think this is more what you were hoping for. The success of manipulating an individual lies in your ability to project what it is you want them to think, feel, say or do. The “theatre” of spell work is unimportant in this area. Fancy wordings will only cloud the very simple mental channelling which is all manipulation magic really is. To perform this kind of working you are always best keeping it simple. Take a yellow candle, light it and concentrate your thoughts on your mother as you look into the flame. Imagine you making the request for the phone back, then visualise the thought process she will go through when you ask her. Project the image of you being hard working and helpful into her mind. I usually speak some words into the candle, something short and to the point
“I think you might find
Yourself changing your mind.”
Visualise the intention leaving you, entering the flame and then being sent into the ether by the smoke from the candle
Best advice though is to tell your mother what you’ve told me – I’m sure she is a reasonable woman, point out the support you give her and are willing to go on giving her. Explain why your phone is so important. In my experience most people react best to genuine human decency.