How are you going to transmit transactions though?

Transactions are pretty small, as long as you have some way to relay data to a party that has an internet connection, you can submit a transaction. The party you submit the transaction to does not need to be fully trusted, worst they could do is not submit it to the network.

That's for sending messages, not money

Messages are money now.

You can't send Bitcoin with those messages over those satellites only.

They say you need internet or sms additionally

Yes, I think this information hasn't sunk in yet for the majority of people.