Best mobile deal?

[Dead Eye]

These days it's worth getting as much data as possible and then mainly use Whatsapp.
A lot of people are on it now, and the texts, picture/video messaging and now even calls are "free" (calls to other Whatsapp users).
And it's world wide too.  :thumbup

Be warned that Whatsapp has been looking to introduce a yearly subscription to use the service beyond the first year ( http://www.whatsapp.com/faq/general/23014681 ) - granted it is very cheap still.

However, your underlying point is spot on as internet services are generally a great option. I personally make use of Google Hangouts (though I preferred the Desktop client GTalk until it was discontinued) and Skype on my phone