After exhaustive research using spreadsheets and math and stuff, I have figured out how to save some money on my iPhone bill.
I've had the phone since August, on AT&T's $59.99/month plan, which gives me 900 minutes/month, with leftover minutes accumulating as rollovers. I only actually use an average of 500 minutes/month, so in the time I've had the phone I've accumulated 2,800 rollover minutes.
I thought I'd bump down to their $39.99/month plan, which gives 450 minutes/month. That would leave a deficit of 50 minutes/month, but that rate I figured it would take me 56 months to burn through my already-accumulated rollover minutes.
Wrong. For one thing, there's a twelve-month time limit on use of rollover minutes, after which you lose them. For another thing, you lose most (but not all) of your rollover minutes when you switch to a different rate plan. The rule is that they only let you keep the number of rollover minutes that your new plan provides per month. By switching to the 450 minutes/month plan, therefore, I lose 2,350 rollover minutes and only get to retain 450.
My mistake, therefore, was to wait this long and accumulate that many rollover minutes before bumping down to the cheaper plan.
Here's how I plan to optimize going forward:
- Effective immediately, I bumped down to the 450/month plan. Although I'm averaging 500 minutes/month, in practice that varies between a high of 625 and a low of 350. At that average rate, it would take me 9 months to burn through the 450 rollover minutes that I'm able to retain. However, if I fall below 125 minutes, I risk paying some extra per-minute charges.
- I'll stay on the 450/month plan until I burn down to about 100 rollover minutes remaining. Then I'll bump back up to the 900/month plan for a month or two until my rollover minutes accumulate back up to 450. Then I'll bump back down to the 450/month plan again.
- Lather, rinse, repeat.
It's a bit of work (but not much) to check the status of my rollover minutes each month when I pay my phone bill, and I figure this should enable me to stay on the cheaper plan eight to ten months of the year, for a savings of $160 to $200.