How can i get the phone contact for a seller, i get no response to an email

Yeah this site needs to improve its messaging system. It may not be the seller's fault, chances are they are wondering why no one is contacting them. If you can figure out the name of the dealer, look them up online and contact them directly. If it's a private seller, good luck. You might try reverse image searching their car's posted pics, and seeing if they've posted ads on other sites. If you can determine their home town, search that area's Craigslist postings. CarGurus is just a free listing site, they don't have any involvement in the sellers or buyers, and the site is not without its faults. Good luck!