Xperia Z1 Very low signal

[Atlax01]

Hello! My problem is that that my Sony Xperia Z1 have a very low signal or no signal! In the streets I have maxiumum 2 bar signal but in building like at my home or in school I have no signal! I thought that this is a phone service problem and they have nothing coverage so I changed phone service but the problem doesn't fixed at all! My old phone, Xperia Tipo have maxiumum bar even in buildings, so is this my phone's fault? I'm currently using 5.1.1, but when I used 4.4.4 I can't remember do I had this problem? What can I do? 

[Uliwooly]

Ignore the bars, instead go to 

settings > about phone > status > signal strength > what do you see?

how old is the SIM card?

Do you have the correct APN settings? 

contact your Carrier/network and ask about their network coverage 2G, 3G, 4G LTE

[Atlax01]

Well I have -109d dBm 1 asu inside my flat! My SIM card is 2 week old! 

[Uliwooly]

That's really bad network coverage. 

[Uliwooly · Accepted solution]

Signal Strength  

-67 dBm	Minimum signal strength for applications that require very reliable, timely packet delivery.
-70 dBm	Minimum signal strength for reliable packet delivery.
-80 dBm	Minimum signal strength for basic connectivity. Packet delivery may be unreliable.