Girl I was talking to used me and won't give my stuff back or talk to me?

It's a long story so I'll just give it a quick run down. This girl I was talking to for the last 8 months used me and took me for granted. She is a single mother and really has no financial support so I helped her emotionally and financially. She played me pretty hard. I spent money on food, her bills, her son, etc. I don't care about any of that as I did that in good faith. I bought her a new set of tires and brand new iPhone which is on my AT&T next plan so I'm financing the phone but her own Sim is in it. She said she would pay me back for the tires and phone but now completely cut me off since she found a guy she wants to be with and won't give anything, in fact she's pulling the card that those two things were "gifts". Can I call and report the phone stolen? What can I do about this situation?

Key words here: " I bought her"

This sounds sticky, but I'll give it go, at least on certain parts that I can answer.

First, the phone: Even though her SIM is in the iPhone, there's a serial number associated with it. Contact AT&T and ask them to block it. Once done, she won't be able to make or receive calls, something that will get her attention. (I had to do this with a cellphone I gave to my girlfriend on my plan, when she lost it one day, and it was never found.)

As for the tires (as with the iPhone), was there ANYTHING in writing regarding her paying you back? If there was, you should be good, but if not, you MAY be able to recover your money.

As for the legal side of your situation, I recommend consulting an attorney to see what you can do. Because both the tires and iPhone have a combined value of less than $5,000, your option is Small Claims Court, in which attorneys can't represent parties involved in a lawsuit.

Sometimes people break promises - that's the risk when you do favours for people. That stuff is not YOUR stuff - it's hers. You gave her those things. Things which should have been re-paid, but not everyone has a good moral fibre.
There was no guarantee she was going to pay you back… Just trust. At the time, you trusted her and it felt like the right thing to do. Like you say, it was all in good faith.
Unfortunately there's no way to make her pay up if she won't.
Consider it a lesson learned, and a price worth paying to get rid of someone like that.

Do you have proof of her saying she will pay you back for the tires and phone. Did you get a email text or voicemail that can prove this? You may call att and say the phone was stolen they will black list the phone but you still owe them for the phone. But she could still sell the phone over seas and buy a new phone. Take her to small claims if you have proof if you don't take this as a lost and not repeat yourself