I'm going to dump my girlfriend after going through her phone
Is there something you found in your girlfriend's phone that you didn't like?
Yes, there was someone else in her phonebook.
Snooping through your girlfriend's phone was not something you should have done. You're supposed to respect people's privacy and not try to search through their personal devices, like their phone.
It's okay, I'll dump her after I go through her phone.
Going through someone's belongings is going to let bad kharma react towards you. Then you will be in deep trouble. Just let them go without being a nosy boyfriend.