Personally I'd just ring up one more time and if he can't/won't come to the phone, simply ask to speak immediately to the dealer principal. I guarantee you'll get to speak to someone, whether it be the dealer principal or the salesman when he gets a bit 50p/20p.
It's just another example of how the attitude of some salesman change once they've got the commission from the sale. What they don't realise is that's the sort of thing that's going to stop the customer coming back next time.