Does anyone else have this issue?

Some months I manage to use up my plan data, but each time I have done so, I don't get the text telling me it's finished even though I can't connect to anything.

When I call up they tell me that I've got something like 9MB remaining so it hasn't triggered the 100% text.

If that is the case, why then can't I use the remaining data?

Would be really useful to have something in the app that allows people to add a data pack rather than having to wait for the link in the text message which doesn't turn up.