Merely to add funds to an account, the family or friends of inmates must pay a service fee. I have an account myself with the prison phone giant Securus so that inmates I want to keep in touch with can call me. In February, I’d loaded my phone account without any fee. Then, a few weeks ago, I was charged $6.95 to add $5 of call time. So, the $11.95 that used to buy 49 minutes then purchased only 20.

It is hard to determine exactly how the fees are being applied: The commissions system is opaque, with the prison itself collecting a portion of the companies’ revenues, leading the companies to charge more service fees to an inmate’s phone account to make up the difference.

These fees are an additional money grab by the phone companies and the prison commissions system. There’s a fee to create an account, a fee to fund an account, even a fee to get a refund. The companies are also taking advantage of a loophole in the F.C.C. order that allows them to add special fees for single calls by a user who doesn’t want to set up an account with them. For the “PayNow” option from Securus, for example, the call cost is $1.80, but the transaction fee is $13.19. Before the F.C.C.’s order was implemented, ancillary fees added nearly 40 percent to phone call costs for prison customers.

Earlier this year, while researching for the Prison Policy Initiative, a Massachusetts-based think tank, I discovered that, partly to offset lost revenue from the F.C.C.’s rate-capping, inmate call providers were making agreements with financial service companies like Western Union and MoneyGram to share the money-sending service fees for purchasing phone time.

The phone companies’ strategy was clear before the F.C.C.’s rate cap kicked in. Last year, Securus acquired JPay, one of the nation’s largest prison financial services providers. JPay handles financial transactions for 70 percent of prison inmates; its fees are as high as 35 to 45 percent of the money being sent. JPay could potentially charge a fee to create a JPay account to pay the service fee to load a Securus phone account.