Urgent! Disable touch screen during calls

I've tried putting the phone in sleep mode. The sensor is SO sensitive that any time I move my face, I'm risking the call being hung up. I have extremely important calls this week (just got the phone 5 days ago) and I have yet to have a phone call that doesn't hang up when I'm on. My cheek or face keeps touching the "hang up" button.

Is there an app or some way to completely disable the touchscreen during calls??

Please help!

thanks for your response. The sprint store tested the proximity sensor - it works, so I don't know. I didn't cover it up wit ha screen protector.. do you have any recommendations of what to buy?

Putting my finger over the prox sensor works, but I can't hold it there for a long call. The only thing that has seemed to work is to take or make the call, press the home key, and then put the phone in sleep mode. That seems to work. It just seems like a lot of hoops to jump through just to have a phone call. I'm surprised that with such a sophisticated phone, it doesn't have an intuitive option to disable the touchscreen.

Is there a setting to adjust this proximity sensor? This happens to me occasionally and it's really frustrating - so I feel your pain!