Over the years, I cannot count how many irate customers I've heard of who scream "We expected a $50 bill last month, but it was $3000!"
Sadly, it is their own fault, not mine, not the maker of the cellular device.
They are at fault for NOT making use of the tools their cellular carrier provides - or they have the WRONG carrier if the carrier lacks such tools! Any good cellular carrier must allow you to set up daily limits, which cause an email or text message to be sent if breached.
For example, this week one of my $14-per-month devices was on it's way to cost me $182 in overages. What saved me? The right tools doing the right job!
My cellular devices are handled by Kore Telematics and I make proper use of the tools which they give me. The device in question has a 10MB account, yet I normally see from 50-80KB of traffic per day, which is 2-3MB per month. Therefore I turn on 2 alerts within my Kore Telematics web portal - I am warned if the device uses more than 100KB in a single day, or if it is on track to use over 3MB per month. It recently did so. When I received the email alert, here is the DAILY summary, where I have circled the start of the offending days.
Oct 21st had 1168KB of traffic, with over 1000% too much. I had accidentally enabled a function within the device which was creating traffic I neither wanted nor valued. The 1.168MB listed is actually only for 2/3rds of the day, so a full day of traffic would be closer to 2MB, and clearly my 10MB cell plan can't sustain 2MB per day every day of the month!
I turned off the offending feature, and my usage will drop back to the expected range.
Here is the Kore monthly summary, which is estimating the monthly total.
The What-If:
Now, consider what would have happened if I had NOT seen this alert. There were 10 days left in October, so I'd have an extra 20MB of traffic on my 10MB/month cell plan - so probably 13MB of overage since I have a 7MB 'buffer' to begin with (I expect 3MB of 10MB to be used). On my 10MB plan, I pay $7 per MB for overages. So 13MB of overage in October would cost me $91.
However, I would not have seen the cellular bill until the 10th or 11th of November, so another 10 days and 20MB would have already been logged in the month of November. Had I noticed the bill when it came and fixed the problem on the 11th of November, then I still would have had roughly a $91 overage on the November bill (20MB + 3MB - 10MB = 13MB).
Moral of the Story:
Make sure your cellular carrier gives you access to usage alerts - and use them!
Discussing my adventures in "IP-Enabling" commercial devices that don't always appreciate being liberated from serial or Ethernet. I have been Ethernet-enabling serial devices for over a decade. However my current job involves putting Ethernet devices up on cellular (as in cell-phone) machine-to-machine data plans. I currently have a public demo site with with Rockwell, Modbus, GE, Siemens, DNP3 and other industrial PLC/devices up on cellular.