What is the true dropped calls rate when in the test it was found to be   zero?
  We study the distributions of dropped calls rates for different wireless (cellular) carriers in different markets. Our statistics comprises over 700 different market/carrier combinations. We find that the dropped calls rates distribution is very close to lognormal. We derive an equation for the most probable dropped calls rate for particular carrier in particular market, which depends on the number of dropped calls observed, total number of calls and the parameters of the lognormal distribution. We apply this analysis to blocked and "no service" calls as well. 
M.V. Simkin and J.Olness