Should I include a set number of minutes in my plans or charge per minute?

Many agencies include a set number of minutes in each plan, for example 500 a month on one plan and 1,000 on the next, and use that to move customers up to higher plans. The advantage over charging per minute is breakage: not every customer uses everything in their package. One might use 200 minutes and another 300, so the average comes out below 500 and you earn extra margin on the minutes nobody used.

You can do the same with an add-on package, for example a 1,000 minute add-on. The customer pays for the whole package, and since almost no one uses exactly the amount in it, some of it goes unused.