make sure you "do the math" both ways before cancelling or changing anything...
Free Dining is really just one version of a Disney discount. Sometimes it's the cheapest way to do your Disney vacation, but other times you can get a cheaper price by putting together your own "package" and just paying cash for your meals. It really depends on how many people are in your party, which resort you're staying at and what percentage your room-discount is...as well as do you really want to eat the way the dining plan works? Price out both version..it might be cheaper to keep what you have.
For example, if you're staying Deluxe or Villas, chances are your room-discount is substantial...and you'd probably find that paying the full rate for your room to get free dining would cost you quite a bit more than keeping the room discount. If you're staying in a value resort, and your room discount is small, chances are the free dining would be a better deal for you (though free dining at values is the Quick Service plan...if you're wanting table service, factor in the cost to upgrade to the regular dining plan.)