The importance of getting the right sim cards and keeping control of them in the field of remote monitoring when using the mobile phone network cannot be over emphasised and this was recently highlighted on a system I have been involved with for a valued client (who will of course remain nameless, as will the network operator in charge). The system we were implementing was not overly complicated, just sending an alrm signal from one place to another using a GSM data (CSD) call. In order to try and save some money the client wanted to supply the sim cardss - as so many large organisations do they like to think they have a good relationship with the operators and get the best deal around. They may have the best deal for voice calls and text messaging but this may not suit the needs of a telemetry system. Anyway, the system went in, all was well and we had a happy customer. After a few months the system stopped working so I got in my car and drove the 3 hours to site only to find the sim card had been disabled. I'm not sure whay this happened but I suspect it was someone at my customers not knowing that the unit was and thinking it wasn't needed. The sim got reactivated and the system was working once again, and did so quite happily for another few months until the call came. Again I got in my car and drove the 3 hours to site - I like to think I give a decent level of customer service. This time I found the sim card was active but the data function had been disabled. I was a little perplexed and popped the unit into my phone and became even more perplexed. On the screen I was told I had an answerphone message so I duly listened. I actually had 6 answerphone messages and these were not the usually squawks you associate with a data call but peoples voices. These were genuine messages from friends and family for Mr A N Other - as well as messages from the operators customer services. I had to dig a little deeper, which was by no means easy nor quick, and found that the data number we had been allocated had actually been reassigned to a pay as you customer. I'm sure Mr A N Other was not best pleased with the situation - I know I certainly wasn't. The moral of the story is take control of your sim cards - don't let it to chance. The cost of my time and travel vastly outweighs any saving that may have been made on using their own sim (if indeed there was a saving here). We actually have control of sim cards number allocation and activation ourselves so we can keep control for our clients. We become a single point of contact and responsibility and I suggest you use a telemetyr supplier that has the same facilities.