It’s a marketing Gimmick, there are no free FREE calls, you end up paying for the DATA consumed for calling, hence it is very challenging to meter the voice calls, which gets passed through system as data usage. Hence it’s no brainier to say voice calls are free. However the data it consumes shall be charged. Call quality is up to mark. Besides so much drawback I must say its worth using, data packs are very cheaper as compared to other rival companies.