I've been using www.voxbone.com for almost a year now , service has been extremely good. They are a bit more expensive compared to DIDWW, at ~26 dollars against 20, and the setup fee is higher too. However, I know the voice quality from Voxbone has been excellent. If someone here can chime in and tell us more about DIDww, then maybe I'd consider switching as well.
On balance, nothign could be as cheap as BrainTel, I guess its like 150 rupees/month, thats just ove 2 dollar a month... but again... you get what you pay for