R. KELLY CANCELS CRUISE TOUR ‘I DON’T SING FOR FREE’

R. Kelly just cancelled his highly anticipated act aboard a cruise ship ... telling TMZ it's all because the company couldn't cough up the cash they originally promised.  If you didn't know already ...  a company called Concerts Cruise LLC hired the singer to headline their "Love Letter" cruise ... where he agreed to play two shows during a five-day trip in October, sailing from Miami to the Caribbean.