Telstra Mobile claims account due in 2 days is overdue

For 2 days now we’ve been on the phone with Telstra trying to get data access back put on a mobile with no success.
This story actually starts a week ago when the mobile was going overseas and in order to avoid the exorbitant data charges ($15,000 per GB) we barred the data plan.
The phone came back into the country on Sunday and on Monday we rang Telstra and asked for the data to be added back to the account.

“Sure” they said, “no problem. That’s done for you.”
“Great thanks”. So we waited a while but still no data. No emails or internet access.
So we rang back.
“Hmmmm” they said, “not sure what happened but I’ve applied it for you now.”
“ok thanks”. So we waited…again…but still no data.

So I rang Telstra again but after waiting one hour for someone to pick up and take my call I gave up. Sure it was 8 pm at night and maybe everyone had gone home. But it might be regarded as good customer service to let me know that the department was closed!

Rang back this morning and we were told “Ohhhh…There’s an outstanding amount on this account”.
OK that explains it.
“When was it due?”
“It’s due in 2 days time”
“Then how is that outstanding?”
“It’s not, but we can’t make any changes to the account until the overdue amount is paid”.
“BUT IT’S NOT OVERDUE!!”
“Sorry, we can’t make any changes.”
There doesn’t seem to be a good explanation here…which is typical of Telstra.
Anyway, I called a Telstra rep I’m familiar with who rang the connections centre for me.
5 minutes later he called me back.
“All done.” he said.
“Thank god.” I said, “Did they say anything about an overdue amount?”
“No nothing. Just switch the phone off and back on it should be fine”

If you know why a bill that isn’t overdue is stopping changes from being made to the account, can you please fill me in? Because Telstra can’t.