A: Hi John, No we do not charge for the first 1k service message.

Here is a explanation below:

Service message: if a prospect initiate a conversation then its called a service message. When someone initiate a message first you can send response without any charge.

Receiving message are always free. For upto 1K message if you respond its free. But after that threshold if someone message you and you respond then meta charge for that message. Hope this make sense to you. So basically, meta do not charge you for receiving message but charge you for sending ( except for the first 1k service message ) . I hope this make send to you.