Blackberry Curve disconects call when I remove from case

[rainbowriver]

I have the leather slip in case from Blackberry. When the phone rings I take it out of the case and it disconnects call.

If it's not in the case it works fine.

I'm on my second case and the same thing happens.

Please help as I got this phone for Christmas last year, so for nearly a year if anyone calls me I can't answer but have to call them back!