It doesn’t matter if she says she trusts you or if you’ve never even acted strangely, you can bet your life that when your girl has a chance she looks through your phone at your call history and your text messages. You have two options with this:
Delete text messages and calls. This can be laborious and there’s always a chance she will get ahold of your phone before you see that last missed call or unread text message. If she see’s a call or message from a girl she doesn’t know, she will be all over you.
Another downside to this method is your cellphone bill. With most carriers it not only comes in the mail, but is also available online and it lists every call you’ve made, when you made it, and how long the call was. If your girl has access to the bill she will be checking it and she will notice that 20 minute call you made to a strange number at 3AM.
The best thing you can do is get a disposable phone. A tracfone is what I use. You can get a phone for 10 bucks, service for about 5 bucks a month. No contract. You don’t even need a credit card. No traces, perfect. Use this phone to communicate with your new girl. Now you can not only communicate freely with your hookup; you also don’t have to be worried about your girlfriend finding anything in your main phone. Keep the tracfone on silent mode stupid… You don’t want a mysterious second phone ringing or beeping one day.
Don’t ever lock your main phone!
If you lock your main phone and she tries to look through it she’s going to instantly suspect you’re hiding something and start digging into things more and keeping a close eye on you. You don’t want this. You’re going to appear doubly guilty if you haven’t locked your phone before and you suddenly start.
Advanced: Turn that shit around on her.
If you just feel like messing with her for looking through your shit, try this. Lock your main phone ( you went and got the tracfone so there’s really nothing to hide, right? ). Now when she see’s this lock she may be confront you right away even though it means blowing her cover. When she confronts you turn it back on her and ask her why she’s looking through your phone. Now unlock it for her and tell her to look. Make her do it right there. When she’s see’s nothing is there, really lay into her and tell her how you feel violated and how you can’t trust her. You only locked your phone to keep people at work/school/gym/etc from messing with it while you’re in the office/lab/shower/whatever. Not only will this get you some trust points, she might try to make it up to you in a “creative” way.