Nokia 5130
Headset problem

I buy Nokia 5130 Xpress Music in last week MARCH. Now I face a problem with my Nokia set, every time when I call to any no. so just 40-50sec. my connectivity automatically cut and second time not response to coverage area. So please tell me what the problem with my Nokia 5130 handset is. Is it big problem? Why my handset atomically cut to connectivity?

Thanks