Had a very similar experience to you recently, made an offer on a property, which I knew was pitched low to gain interest in it. Made an offer, never got back to me, called each morning and afternoon looking to speak to the agent, made a note of all the times i called and the promises made to call me back. This was for a complaint I was adamant to make for what I saw as totally unprofessional in dealing with potential purchasers.
I dont expect them to become our friends, but a little courtesy goes a long way. It seemed like it was returning to the bad ould days a few years ago when all you needed was a suit, clip board, mobile phone and bad attitude to sell a property.
Any way, it got to the stage the receptionist recognized me by by number since I had called so often, greeting me with, hi there LS, dont tell me **** still hasn't called you back yet.
Bottom line, I sale agreed the property a few week ago. Dont shy away from calling them again and again. The property is only worth so much, I knew if they tried to ramp it up on price, I was happy to walk away. But it will sell for market value.
Oh, and the call times sheet, it has been filed away under .B. since I succeeded in getting the property.