[dagw]

being sent by a method called 'SMS' which isn't very reliable, particularly when phone signal is poor...

Not that it is relevant to overall point, but this is the exact opposite of my experience. I've been in plenty of situations where it is impossible to make calls because the signal is so bad, but communicating with SMS has worked perfectly. As my signal gets weaker and weaker, SMS is always the last thing to fail.

[gvurrdon]

Interesting. I don't think I've noticed that, but I have run into various issues with SMS when there's poor signal. On one occasion I could receive but could not send, just at the perfect time when someone was waiting for me and I was unable to get to them.