Help me with a few things?

Since 7th grade I have wanted a iphone and 9th grade I used a flip phone because I was in high school, and then when my mom got my dads old iphone 7 plus I got her old iphone 6 early before 10th grade started because my posture was wonderful, and that is how I was able to get a phone because my posture has to be good to have a phone. I have had my phone from July to the end of October because November I lost it because of my conversation skills were terrible and that has been approving really well in the past 3 months I have had my phone gone for. Next was my posture also known as body language which was another one I got in the end of December I had to work on, but it was not going well until my Mom and Dad said I have four weeks and I could have my phone back which was the last two weeks of January and the first two weeks of February. When the four weeks were up I asked if I could have my phone back and my Moms same answer to me if no because your posture is not good and this her way of telling a lie to not give me my phone back. She also says to me there's not set date or time that you will get your phone back because you will get your phone back when your dad and I say so. What should I do because I really want to talk to my friends not just my one friend through our school email and I don't want this to go through my summer where I can only hang out with one of my friends not any other of my friends because my mom is still trying to keep my phone from me. Help me out.

Added (1). Help me out with what to do with my posture in a week or a week and a half and how to get my phone back.

How can I get the time back I wasted reading this nonsense

Posture must mean your parents' way of judging whether you've been a good kind of child as far as your general attitude is concerned.

Only way to get it is to make sure you do what you are supposed to do. Posture? Conversation skills? Etc.

However that being said, it is NOT your phone if you do not pay for it. It is still not your phone if you are under the legal age of 18. You can't buy a phone unless you are 18 due to contractual agreements with the provider as well as credit check(assuming you are in the USA and Canada and parts of Europe that I'm aware of. I'm sure most countries have similar rules.)

So, if your parents say they will give it to you when they are ready, my suggestion is to leave it be. Unfortunately you are stuck until they are satisfied with your behavior? Posture? Etc.

Your mom sounds like a narcisist who will use whatever excuse available to keep you from having what you want. It makes her feel powerful. So, the next time it comes up and she says no, say something like, "It's okay if you can't pay for another phone line. Just say that instead of blaming me for it." Note: You WILL get in trouble, and she will probably wind up screaming in your face about how much money they have, etc etc. Just nod and say, "Really, it's okay. You don't have to feel bad. I understand phone lines are expensive." Just refuse to believe anything other than she is keeping it except because of money. It'll drive her nuts and she'll find some other way to twist you in knots, but at least you'll have your phone back.

Just try to have good posture so you can get your phone back