Koodo phone keeps turning off when I send a long text?

[blackrose]

K, I just got this phone a bit over a month ago and it's been working great for me so far. Lately though, whenever I send a text that's more than 1 page long it turns the text into a slide show text(when u scroll down to see the whole text) instead of just sending pages. Now this hasn't been a problem so far, but a few days ago, if I tried sending a long text message that turned into a slide show text, my phone shuts down then turns back on. I haven't drop my phone on anything really hard, just my bed, and this hasn't happened before so I don't know what to do. I can't even try and change the message because the phone says it was sent and you can't edit a sent text. I don't know if the company it's from has anything to do with it, it's a Koodo phone, flip phone kind. Please help!