I'm having a strange issue on my 6s, running iOS 10.3.2. In the storage pane of Settings, Messages is shown to be taking up around 700MB of space. That is impossible, however, because I have deleted all attachments from almost every conversation, and with the few remaining attachments left, it should only be around 10MB or so. I have restarted my iPhone and double-checked every conversation. Any other suggestions?