Amantel is one of the company which provides one of the cheapest calling across the world. I have used their services and it has good sound quality but worst customer services. The staff in the customer service are not properly trainer nor then they have proper communication skill.
I had worst customer service till date and they are not in a mood to trainer or learn how to customers. I don’t think anyone can beat the call rate of Amantel in US but only providing cheap calling will not let them stay in the market they need to learn about communications