Need a suitable punishment for an 11 year old phone thief.

[NeedHelpPlease123]

My daughter stole her friends iphone last night, I searched her coat and bag when I found out her friends phone was missing, but she had already hidden it elsewhere at that point. I asked her many times if it was her, she swore it wasn't her and said it was probably the girl's little sister, as the sister was playing with it.
The mum knocked at my door this morning and asked if my daughter had the phone, I said I checked her bag and coat and it wasn't there etc.
Shortly after my daughter asked me where something was, I opened her drawer to find not only one phone but two! Both were stolen from the same girl.

I took the phones to the school and explained what had happened to the head of year etc, so they know what had happened and could deal with it internally and so the phones could be returned to the girl.
(she is excluded from lessons).

I need some suitable punishments for outside of school as this I can't think of anything suitable to match how awful her behaviour has been.

She is already grounded for 3 months for going to said friend's house without permission and not coming home until 8pm.

I need suggestions for individual punishments for stealing phone one, stealing the iphone, lying when questioned about it, stealing from a friend, and making me into a liar by misleading me.

The child described above that just stayed out all night because you were going to get into trouble anyway was me. I was older admittedly but still at school. My parents were stricter than the house master was on the boarders at my school. I stole because I was surrounded by people that had more than me because my parents felt they were teaching me a good life lesson about being individual rather than wanting to fit in with my peers. TBH if my parents had even listened to me rather than talking at me they would have had many less sleepless nights.
3 months seems excessive. I have a young 13 year old now but at 11 had a cheap smartphone and access to the internet. With lots of monitoring and discussion about how to stay safe. The danger with so many restrictions and harsh punishments are that she will just lie more and hide more from you, and where do you go from here? How do you punish the big stuff in years to come if you punish so hard now?

I have no idea what punishment I can give to correct that behaviour.
This is where things are going wrong. You can never punish a child into behaving better. Punishment tends to make children more creative in how they get round rules and devious to avoid getting caught.

I get the feeling there is a big gap in your relationship. It doesn't sound like you are communicating that well or listening to her. You are treating her like she is a much younger child. You say that she has no need for internet access - have you ever asked her? I bet she does want it. I wonder if that's why she took the phone. You need to listen to her and take her feelings seriously. If you don't her behaviour will demonstrate how she feels.