Whenever I start to compose a new text message on my iPhone 6 to send to someone, as soon as I enter their name in the To: field the last text that I sent or received from them appears in my message editing box. I can add new material at the bottom but cannot delete what was exchanged previously. This is causing my messages to people to keep building up in size with the total message being everything I ever sent to them plus what I'm sending as a new message.
How can I just send them a brand new message without the entire conversation with them over the past year being prepended to it? I don't want to delete the previous messages from cache, just don't want them to be included in the new message.