I am posting this reply using the Mtnl 3G connection with the Rs4500 for 6 months plan from Delhi. I got this using ngpay. With Ngpay we just have to choose the option that says data plans and enter amount and it goes through.
I have only used ngpay using the application that I have on my mobile phone. I am not sure if you can use it from desktop. I have been using my debit card with it but I dont see why it wont take a credit card as every company does.The best thing I like about ngpay is that unlike many companies if you make a mistake like enter an idea number and try to recharge it using the vodafone option or the transaction doesnt go through you dont have to chase them for refunds as they do it all automatically. The last few years since Ive been using them I have never had a problem with them.