Excell Communications (AL) interview questions

After a great interview, but multiple follow up emails re: application status, I was given an offer. I had a few questions and had requested a higher salary and had questions about benefits. They did offer my original requested salary, I provided during the initial phone call, however, that salary was provided for a less experienced position. I accepted the offer on Tuesday but hadn't heard back re: onboarding. I gave my employer 2 weeks notice on Friday and on Tuesday, they called saying the company is closing the position and taking back their offer. Beware.