I have been charged for unreceived messages

Thank you for your reply.
But for example, my phone was turned off whole day yesterday and I checked my account from PC. There are charges for some messages on yesterday. Why should the messages be considered as delivered? Where are they? If T-mobile says the message was really delivered, is there the way to retrieve the message when I turn on the phone?

I think I was charged over $50 for these blocked messages in last 12 months. How can I stop this?
My phone usage is minimum. It can be less than once a week. So, I usually turn off my phone. Could you tell me if you have any suggestion?