Funny thing, I just got a letter today from Sprint about this very thing. It said "You are receiving this letter because a recent review of your Sprint Mobile Broadband card ... indicated an unusually large amount of roaming use over a three-month period". It cited a section of the "Sprint Subscriber agreement" where it shows that Sprint "reserves the right to limit throughput speeds or amount of data transferred; and to deny, terminate, modify, disconnect or suspend service if usage either exceeds (a) 5 GB per month in total or (b) 300 MB per month while off-network roaming" (a section that was not in the agreement when I signed up, but, was added recently).
I called Sprint to get more info and, the rep I spoke to could not tell me:
1 - Which three-month period they were talking about (the rep said it had to be some time between January and May).
2 - How much roaming or roaming data usage they actually detected (there could have been a lot ... two weeks storm chasing in May and streaming video during that trip)?
3 - How many failures to abide by those "guidelines" would actually cause any disconnections (but, she did say that an isolated event would not be sufficient).
She did say that the letter has been sent out to a whole slew of customers to ensure that they are aware of the guidelines and also said I can cancel without penalty and even get a month's refund. So, I also will be checking to see if I can get a better deal from a different carrier (not sure if Alltel will actually accept me as a customer if I use my own address).
My guess is you silently rack up charges.
