Singapore to Darwin - Question

Bit of a strange question but would really appreciate the reassurance.

My 78 year old mother has just been told she's got to go in for a major operation in the UK - just as we are at sea and half way between Singapore and Darwin.

Can I rely on getting a mobile phone signal 2 days out from Singapore and with 2 days to go before we reach land in Darwin?

It's too late to cancel the cruises so Im looking for re-assurance that I can still get in contact (she cant use internet or text messages).

We will be on Voyager of the Seas.

Thanks in advance.

Another option perhaps.

Do you have Skype or something similar ?

We have used ship's internet and then Skype to call landlines.

Thanks for that - its an option I hadnt thought of.