Nokia lumia 720 losing network coverage frequently issue

[WPCentral Question]

I am using Nokia Lumia 720 for last 6 months and it was a great phone firstly i can tell.
But it is having a serious problem now. It loses network coverage frequently and we have to search for networks manually
once it lost. This is irritating me because nobody getting me on time on call till the time i could find it.

Surely this has started after some phone updates and what to do with this? Please provide any proper solution.

Thanks