My boss is withholding my bonus saying it never existed

I need help. I signed onto this job under the impression I was receiving a starting bonus. I’ve been in this job two weeks now after continuously asking when I would receive it. My supervisor says what they really meant was a commission sale bonus so I’m not getting that money just for accepting the job offer as I expected and received verbal agreement to. I’m livid, this is false advertising. Is there anything I can do about it?