What happens when my girlfriend turns off her phone and ignores me?

Since you think you are not wrong, this matter can have nothing to do with you.

According to my analysis, besides being angry with you, there are several possibilities:

1. She has been in trouble recently and is in a bad mood. She doesn't know how to handle things. So, she chose to turn it off and even ignore you. Maybe she is afraid that she is in a bad mood and can't help losing her temper with you. If so, you can try to ask her if something happened. Why has it been neglected recently? Say it, and we'll work it out together, okay? Something like that

2. She likes another person, or she has done something wrong to you, she doesn't know how to face you, or she is afraid to face you. Maybe she is giving you the cold shoulder in this way. Wait until you give up on her slowly or can't help but break up.