Default nexus 5 signal issue

Hi Guys,
I have a 16gb Nexus5, with stock 4.4.4

Have a strange issue of signal getting lost during the call.
After every 5-7 mins the calls get dropped as signal level goes down to zero.
Is there any work around for this? Anyone else facing this issue?

PS : using the device in India, with Vodafone network.

Regards
Mukesh