You are just paying $10 monthly on unlimited India calling and you can install on two mobiles like extensions. Currently, They are offering $7.66 plan for 3 months subscription, so you are paying less than $4. I can easily say Rebtel.com is a winner and no need to look at another site. Still, if you want then you can refer other site mentioned below.
Callinida is another great and cheap way to call your loved one or anyone in India. They have very attractive price $5.33 per month for 3 months subscription and then regular charges of 8.99 per month.I am not sure if you can install on two mobiles like an extension so I am giving this the second rank. Please try and let others know if it works in two mobiles.
Google Voice 1 cent per minute
Google has solutions for everything. For Voice its Google voice. It is an online calling service by which you can call any phone in any country at very cheap rates. Google voice offers low rates for making international calls from USA to India. The rate per minute is 1 cent for mobile phones. You need to have a Google voice account for making calls.Google voice also offers voicemail services also.
Vonage $14.99 per month
Vonage is costly in my opinion because it is offering 6-Month Promotion at $ 14.99 /month for the first 6 months with One-Year Agreement after that 27.99 / month plus taxes and fees (Tax and fees are approx. $9). Though it’s very popular in our Indian communit. I personally used more than 2 years. Vonage service requires Vonage adapter, standard or cordless phone and a broadband connection. You can buy the Vonage adapter and cordless phone free from Vonage website. It offers unlimited calls to landline and mobile* numbers in more than 50 countries. For India, it has the unlimited talk time for both mobile and landline phones. .
Keku Mobile App, $9.95/ Month
KeKu offers an easy, reliable and inexpensive way for you to call any phone number in the world. When you’re in your home region you can make a call through KeKu SmartDials technology and use your regular minute plan to call a local number assigned to your international contact. KeKu then will automatically connect this call to the international number. You can also choose to call internationally via the Internet by using WiFi or your data plan while you’re traveling. Check Keku’s official website for more details about this service.
Skype 1.5¢/ Minute
Skype is an application that will help you make audio and video calls to anyone via computer or a mobile phone. They also have a paid option with which you can make calls to landlines and mobile phones to any country. Skype to Skype calls are completely free. For this the other person you are calling needs to have Skype installed on their smart phone or computer. But for calling people on their landlines or mobile phones in India, you need to have a paid subscription with Skype. They have two options – one is pay as you go where you just pay for whatever time you talk and the other is a monthly subscription. Details here.