MiFi malarkey

Greetings fellow customers,

I am a newby to MiFi, however, I need need a temporary WiFi connection whilst living elsewhere for about a month.

I have unlimited text/calls and 60Gb a month Smarty on my mobile. How do the plans work? Can use my existing sim or have to purchase a data sim? Alternatively, do I tether the phone? The group plan appears expensive for my needs.