Matrix Sim Cards are by far the best services for international sim cards in Delhi--- I had to suddenly fly out to Shanghai for work and wasn’t up for using a local sim card there after my last experience in that country. It so happened that at the Delhi airport I came across Matrix Sim Cards and I pretty much liked the idea of carrying an international sim card. Its top notch in convenience, since i got to share the number even before I flew out. The convenience of an English/Hindi speaking customer care was the best feature in the deal. Once I landed and switched my sim to the matrix sim, I had no issues with either making calls or attending them. Its so much better when you know that the service provider can understand your language especially in a country like China. I accidentally used matrix sims, but definitely recommending them for travels.