Charity lacking in IT sense??
But they have developed and deployed a miniature tracking device....
while in house IT may not be to blue chip standard, they did manage to find enough skill somewhere to bring this project to fruition - if the data tracking module was designed and built by the charity, then one would assume the knowledge would be there to use a SIM that would have some controls on its use...
If, and i expect this is the case, the tracker was bought in, then during the sales and training for the unit someone should have impressed on the security features of the product and supplied details of validated carriers and sim types.
Then... well, im no bird expert, but I would expect that if one of my subjects had failed to move for a few days that it was probably not in a good way... and after a week of no movement Id have probably written off the creature - prompting the closure process for that particular tracker.
Its unfortunate, and a learning process, but these things happen...