This is exactly what NOT to do,unless you're quitting a news paper route,and you're 14.Like others have said,be short,direct,no lengthly discussion,and lastly,agree to honor your committment to play the EXISTING gigs,and not future ones,not yet booked.That's what responsible adults do.Maybe you can try quitting like a notice I gave to a place where I once worked.
I walked into the office and said, "I'm giving my two-day notice, I'm quitting TO-DAY!!" And I walked right out the door. The looks on their faces will be remembered always.
Be a pro,look them in the eye,and be firm ,and DON"T leave them just hanging.Actions have consequenses,and what you do effects everybody in the band,not to mention your rep.which means a whole lot in the biz.