Welcome to the guest questions forum.
If you are plugging your phone into the wall charger and it's showing USB, there are several things that could be wrong.
1, the charger is faulty. Be a good idea to replace it or try one of your friends' cables.
2, the charger is not putting out the proper amperage to register as anything except a USB connection. See #1.
3, the battery could be faulty. Also a good idea to replace it or borrow a friends' battery to test.
4, your charging port could be faulty. Unfortunately, unless some piece of fluff is in it, the only way to remedy this is to replace the phone.
5, if you have rooted the phone, it could be stuck in a non-fast charging condition. I'd recommend a factory reset to fix this issue, unless you know what ROM you have and where to resolve this issue. (If it's even possible.)
Hope that helps!
