[Klotar]

It took until this morning to resolve the issue. In the time since the original post, after numerous attempts to send service books, register HRT, etc., even upgrading to a new OS, restoring service books, etc., nothing worked.

The cause of the problem was indeed that International Roaming was not enabled by Airtel (thanks for the tip, JS), but since she was already abroad, it was near impossible to arrange to have International Roaming enabled because 1) the account was relatively new, 2) they required a deposit, and 3) a written request had to be submitted.

Finally the roaming was enabled, and emails flooded in, service books [finally] arrived, wifi started working, network welcome message, etc. and SOS went away.

Of course, to avoid the high roaming charges, we now have mobile network off, data off and wifi on but all is working as expected.