Why does my 3g and WiFi barely work on my Sony M4 aqua?

[AC Question]

Hi, I've had this Sony m4 aqua now for about a month and ever since I've had it the 3g doesn't work well. I'm meant to have 4g Aswell but no matter where I am I can never connect to anything unless it's texting or phone calls. Also, to top it off, when I'm connected to WiFi it works but barely. I can't watch videos on Facebook or snapchat and it runs very slowly. Does anybody have a solution for this? Thanks!
Ps. Everything worked fine on my previous phone.

 

[B. Diddy]

Welcome to Android Central! Do you have a case? If so, how well does it work without the case? If the case is metallic, that might interfere with reception.

Who's your carrier? Did you get the phone from the carrier, or was it unlocked? If you're using an unlocked phone, it's possible that the phone's support for your carrier's network bands is poor (e.g., it might only support one of the carrier's LTE bands, which might not be that common in your area).

When you say your wi-fi barely works, do you mean that the signal is very poor, or that the signal is fine but the speeds are very low? Does this happen on any wi-fi network?