how to store the channel?

I bought a 29inch transonic tv no remote second hand. It was a real bargain it came tuned in. However since then we have more channels available and I've bought a dvd. My problem is once I've tuned the channel in it wont store. So I'm constantly retuning the tv all the time if I wanna watch a dvd or watch a new channel. I've tried pressing and holding the store button and store comes up on screen but once the channels been changed and I change back it's gone. It's got the buttons on the front below the screen it's very basic just a auto tune button then a + and- button for manuel tuning then the store button. I'm wondering if I must purchase a remote to store the channel seems strange anyhow. Theres a sticker on the back the # is GT- 9329
Anyone know what I need to do?.