If I have proof that my previous boss agreed to pay me after I put in my 2 weeks, is it illegal for him not to pay me?

I put my 2 week notice in and was asked not to work the 2 weeks but was told by the General Manager/ part owner (via text message) that I would still be paid for the 2 weeks. I was paid for the 1st week but when I came in for the 2nd paycheck I was told by the GM that I didn't have one and that it was out of his hands and I would need to contact the primary owner. I've called several times and the owner will not return my phone calls. I've been told by several people that as long as I have proof that I was going to be paid for the 2 weeks then legally they have to pay me. Is that true and what should my next step be?