How do I clear google history from my cell phone, nothing is working?

I got the LG620g cell phone. Not one of the fancier cell phones around now, and it's through Walmart's pre paid service called Straight Talk where you buy calling cards every month. I can clear cookies, cache, and I can even clear the browsing session, but nothing is working to clear search engine history like google or yahoo. It only cleares the websites that I direct address in the adress bar. Key words still pop up on google that I have searched for a couple of months ago when I first got the phone. No, I'm not trying to hide anything, my google just gets cluttered too much with previous searches. On all my old phones in the past I have been able to clear google history when I was with Verizon, and any other phone I've used. Does it have something to do with my phone being with a pre paid company called Straight Talk through Walmart? There has to be a way though. It's just aggrivating.