Why do I have to charge twice for sending short messages in groups and charge for sending short messages to empty numbers?

Double the charge for each message, because your message is more than 70 words. If you send 100 words, that is, more than 70 words, 100 words will be the cost of two messages. Although you only sent one number, the operator will deduct the cost of two messages.

If you send an empty number or a stop number, you will be charged. As long as the delivery is successful, there will be a charge. This has nothing to do with whether the receiver receives the message or not.