I have similar question as well.
I am building hosted telephony app, and the question is whether to charge base fee + telephony charges or bundle minutes into the plan.
eg.
$9 for basic plan + 5 cents a minute
$15 for advanced plan + 3 cents a minute
OR
$15 with 500 Minutes $30 With 2000 Minutes etc.
what are general assumptions? What factors should I consider before making final decision?