I have made extensive researches on the subject: I have examined forum threads back to 2008 and looked at almost all the websites which have been suggested as well as the hint that were provided.
Many website advertise free calls but they are using misleading advertisement and in the end they do not give anything away. In the long run, I have found that Skype has the cheapest rates for calling.
In conclusion, I suggest that it is useless to search how to make free calls. In this world nothing is free except breathing and yet will come a day that we will be taxed for it.