Something worth noting is that Telstra don't advertise their capped plans but if pursued they do a great $49 and $79 capped plan. Not sure of the full allowance but included is calls of around $250/Month ?? on $49 & $500/Month?? on $79 Plan.
A few calls on your prepaid or normal account soon add up.
You may have to pay up front (or a monthly fee) above this for a new phone but it can save you heaps in the long run.