I called my cellphone provider, Cellular One West. It took about 10 minutes of arguing with the representative to get her to admit that yes, the change in calling plan could be applied on a prorated basis in the middle of the month, and yes, I understood that that meant that I would not get the full number of minutes the rest of this month. Why was that so hard?
I'd change providers, except that nobody else offers the kind of calling plan I need any more: nationwide calling, and nationwide roaming at no additional charge. I have to be able to call anywhere from anywhere in the US, and the big carriers have all stopped offering that - at least the big carriers that offer service to a Fairmont home address.