Here is my opinion (Maybe there is an attorney or other minds that could add to this or improve on my thoughts I am not an attorney)
1. I would send them a letter stating they have 30 Days to communicate with you or you will quit claim deed back to them, and will relinquish all rights but will not pay any more maintenance Fees due to their unwillingness to communicate with you. I would tell them if they do any further collections or damage your credit in any way you will hold them civilly liable for any damages if you quit claim the property as they have withheld use from you. They have failed to perform with your original contract. Then quit claim it.
2. If you are a member of RCI there are some great Last Call and Extra Vacations you could use.
3. There are timeshares for Sale on TUG, Timeshare Forums, Ebay, Holiday Group, Red Week, Tri West Timeshare etc. Many are very cheap right now and some may even be $ 1.00 or Free. Some owners want out of their contracts and are just glad to get rid of them. Do the research and you will be able to find a great one. Follow advice here on how to buy. Look at the TUG advice section especially Timeshare 101 by Steve Nelson.