Got one job offer, took it, then got another.  Etiquette?
So three months ago I was recommended by my instructor for a pentester position.  He said that once the class was over (a week from then) he could officially vouch for me, since it's not showing favoritism if I'm not his student.  I apply for the position and wait patiently.  I email them back about 10 days later as per my instructor's advice asking if they have reviewed my resume, and got no response.  I figured they had either ignored, forgotten, or lost my app.<p>Fast-forward to a few weeks ago when I apply for a sysadmin position at a local ISP.  Less than three weeks from applying, I am hired before the background check even clears.  I started last Wednesday.<p>Today, I get an email from the first company saying they want to set up a phone interview.<p>I really don't know how to handle this.  Do I play hardball and tell them I was already hired?  Do I ask if they can beat the pay and benefits of my current position?  Do I say I am still interested but have been employed elsewhere?  Do I tell my current boss that I might be considering a better position at another company?