I run a Pi with a Huawei E8231 3g dongle. Once a day, at a specific time I connect to the internet, send a100KB data file and then disconnect.
It will go for weeks using about 100kB a day on a 500MB/month data plan. Then one day 500MB of data disappears during the 24 hour off-internet period. Looking in syslog there is nothing apparent.
The ISP have told me that they can not tell me how my E8231 (Wingle) uses this data. I have read that Huawei do not do firmware upgrades on these devices.
Any suggestions how I could tell what is happening when the device is not connected to the internet would be really appreciated.