<human>: i had recently found out my girlfriend was cheating on me with a coworker. (a friend of mine actually was able to take a picture of them hooking up at a bar, and he sent it to me on my phone). i confronted my ex  the next day, and naturally she denied. i then told her that i had a picture on my phone, as i was handing it over she decided to do the logical thing and destroy the evidence by destroying my phone against the ground. long story short, i took her phone that was charging on the counter and left. I now have her phone with her sim card. she most likely has reported her phone stolen so i dont want to keep the sim card in. 

MY QUESTION IS

Can you summarize the given text in a few sentences?
<bot>: how do i use my girlfriends phone as my own? is there a way to erase her number off the sim card? what are your suggestions