Signal Problem!!

I am using the phone for almost 4 months now, and I've been using it as my primary phone, there is a problem with the network signal for sure! At my home, there are 5 phones and all of them are working fine except for this one! most of the time there is no signal, or really weak and not reliable. Other than that, everything is perfect, but what is a PHONE without the ability to make and receive calls!!!

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