Sadly, no. I tried going through the game without any hints or spoilers, and usually what I do is max out my currency-makers then start buying the most expensive things first then work my way down to the cheapest. Thinking that there was an infinite amount of ghosts to buy, I forgot to buy the last/cheapest phone call before I started to buy answers from Burger's Ex-wife.
Seeing that I couldn't buy anymore ghosts and being at a stand-still for so long, I finally looked up what I did wrong and it turned out that I needed to unlock the Ghost Stock Market before spending the limited remaining ghosts on answers. Is there something I'm still missing?