Call the vet and leave a message for him to call you when he has a minute. I would call the first vet too and have him call you back. I have never been charged for asking a vet that is treating my pet to call me back.
Have your questions written down and try not to be emotional. Clarify your treatment options or lack of them. Ask if the treatment, medication is aggressive? Does he expect the dog to respond to the treatment? Will it keep the dog comfortable? What are your options. Talk to him about euthanasia, if you suspect that the dog is suffering there is no hope, see what he recommends.
Oh, and I would go over what you have spent with the first vet and ask him if he can give you a break. http://www.humanesociety.org/animals/resources/tips/trouble_affording_veterinary_care.html
Good luck
