First, buy a clean notebook and start logging every communication with the builder in the notebook. Every call you make. Every message you leave. Every, although few, reply you receive. Take a few minutes and send the builder a certified letter indicating that they are not demonstrating a reasonable effort to complete the pool and requesting a detailed schedule of work to which they will perform. Request this in writing. Give them a reasonable amount of time to reply to you, like five days after receipt of the letter. Again, send this letter by certified mail. If they don't reply you need should seek advise from the BBB and probably an attorney.