I keep getting calls from this number as well. I am also on the Do Not Call registry. They call every day; even weekends. It is really annoying. No one is ever there and you can't call the number to talk to anyone because it doesn't pick up. Whoever is at 210-802-4398 needs to fix their problem.
Call back gets, "Hi this is Andrew with the Heyl Real Estate in Austin Texas. I'm not here to take your call......" Apparently this division of Keller Realty was founded by Tim Heyl. Here's the web site with his biography and phone numbers. Why not let him know you don't appreciate his unsolicited calls and file an complaint with the FTC's Do Not Call Registry.
Here's the link to Tim's bioagraphy
http://www.kw.com/kw/agent/timheyl
Here's the link to file a complaint
https://complaints.donotcall.gov/complaint/complaintcheck.aspx