I sent the other half a text message today. It arrived more or less immediately. This is quite good going based on my recent experience with Airtel here, however, the amusing thing was the timestamp on the message when it got to the other end.
Both phones said the same time. And the message apparently was not going to happen for another 15 minutes - yes - it was a quarter of an hour in the future.
Either Einstein (and various others) have made some fundamental errors in their calculations, or Airtel have a TARDIS hidden away somewhere - or - possibly more likely - somebody, somewhere has broken something.