If u want really good service then use rebtel.com.It has lot of advantages.its gonna cost u 22c per minute but its worth it. :
i) you donot need to dial access number,pin number,destination number eveytime.They will give u a local number for ur phone no matter where u call.Once u save that number,its just like calling from ur cell phone.
ii)Best connection ever and sound is crystal clear.
iii) U can go online to check ur calling history.
iv) Can recharge ur account through phone, no need to go online or call customer service.
v) Best of all,if u r first time user they will give u 10 min free and if u buy $10 worth,they will give u $20 worth.
SO Try www.rebtel.com