Yeah Im def gonna ask her to block those numbers, but then work would be akward for her and maybe there's the possiblity they would bother her more at the workplace. I know she should tell HR again, but is it really wrong for me to go over and say something to these dudes? (If im not threatening them or doing anything wrong etc...)
In my opinion, yeah that would be wrong of you.
Three possible cases:
1. She would prefer to take care of it herself and is faithful -- getting involved is a mistake.
2. She would prefer to take care of itself because she's actually cheating or wants to cheat -- the sooner you find this out, the better, but actually going to Best Buy and confronting seems a bit much. Just move on unless you're into non-exclusive relationships (though even that would / should be a conversation).
3. She is actually looking for you to "stand up" to show you "care" -- this also demonstrates that she's not really ready for a healthy relationship. Trust issues aren't like a simple disagreement "Oh I love avocado but she Hates it". They can seriously impair a healthy relationship. If she's looking for this sort of response from you, you are enabling her by going down and talking to them. I get different cultures look at this differently, but you'll be better off in the long run by addressing the root insecurity than by being the big bad wolf.
Other notes:
A. Regarding her being unfaithful, just keep your eyes and ears open. Eventually something won't add up (she keeps taking rides on days that aren't rainy / you saw her work schedule and it's different from what she told you / she's suddenly very distant from you and ignoring texts, etc.) and then you can dig deeper if needed.
B. I'm surprised she's actually taking cabs to work at Best Buy. How close does she live? Because a cab can be like $10 easily, which is probably like an hour's work?
C. Have more value in yourself. You're a hard working guy who is faithful. If she leaves you for a cheating married / girlfriend guy, you're just freeing up your life for new encounters.
D. Remember, at the end of the day, you were happy alone. You seemed capable of talking to people of the opposite sex and are focusing on studies -- you probably can find other people.