Telstra Billing Problems

I just got my monthly Telstra bill. Of course there are problems. One of the charges is for a Mobile Enhanced SMS message – A.K.A. MMS. This would be fine apart from a few problems

a) The SIM card is in a device that was turned off at the time.

b) The device is fairly well sealed so it is unlikely that someone borrowed it to make an MMS call.

c) Telstra cannot give me any details on the MMS message.

Looks like the billing system has some corrupted data.