Did i lose her trust? What should i do now?

Here's what happened, i visited my aunts house on during my summer vacations and stayed there for 2 months. In the first week at her house, my phone (iPhone 5s) fell on the concrete ground and broke. My aunt gave me her old phone and told me that i can use it for as long as i'm at her house, but when i go back to my own house, i have to give it to her brother (my uncle) because he wanted that phone for her daughter. I used that phone for the entire time i was at her house and had stored a lot of data and pictures in that phone, and i also got used to it. When i went back home, i gave my own iPhone 5s for fixing and kept on using my aunts phone. The stupid mechanic instead of fixing it made it even worse and messed up the entire touch screen (LCD), he told me that now he would have to replace the entire touch screen which would cost about 150$. I told him to replace it since i had no other option, but he said he was currently out of those screens and that i would have to wait 3 days for it to be back in stock. I kept on using my aunts phone for a whole week. My aunt on the other hand thought that i had handed the phone over to her brother (my uncle) until she called him and asked him about how the phone was working. My uncle had no clue what she was talking about, since i never gave him the phone. My aunt was obviously shocked to hear that and also because she trusted me more than any other kid in the family. How should i regain her trust, i will probably call her tomorrow

Tell her that you just need the phone for a little longer to send the pictures or whatever to your phone once it gets fixed. This honestly doesn't sound like a big deal, if you explain it to her… And btw, you're overpaying for that LCD, should be around $80. Look for a yakety-yak near bye, they have good deals.

You should have asked her permission to take the phone home with you, so I think it would be good to apologize for not doing that.

I advise that you call her now. The longer you wait the more angry and upset she will probably become. Just call her and tell her the truth. She will understand.

You could gain her trust by giving her back her phone, and if you have a lot of sentimental pictures on it, ask the phone place to take them out and put them on a disc, i did that when my laptop broke and the computer place made a disc out of them, they might be able to do that before you give it back

What is done is done. You have to call her As soon as possible and make sure you can clearly explain to her what happened and why you kept the phone.