how do i make my girlfriend understand me more and admit when shes wrong???

well weeve been together for 2 years she is a very cool girl and i love her soo much, is just that sometimes im not saying that always nut somethimes she tends to do something bad and i try to tell her hey why did you do this or something, like sometimes when im out she tells me to call her wherever i go and when she goes out she "FORGETS" to call me and i tell her that why didnt she called me and tries to get mad at me and she persists untils he does it and in the end i have to apologize to her and tell her " you know what, it was my fault, yeah" i always end up daying that in the end of the argument because if it was up to her she wouldnt tell me anything, like right now im mad at her and if i dont call her, she wont call me, until i do call her then shell talk and sometimes she says tha she doesnt want to talk to me,