I'll have to disagree on the 'Poorly Built' argument. I've found the Micro USB port to be fine. Daily charging since April with no issues.
However, having repaired these connectors in a former life, I can say that the surface mount pins on the rear do not lend themselves to taking much abuse, they are so small that the solder joint will not have much mechanical strength. And even if the solder joints survive then it's quite easy to pull the copper pads off PCB.
By abuse I mean wiggling the thing, especially up & down. If it is plugged in and pulled out straight it should last fine.
Anyway, have you confirmed it's the port by trying to connect to a PC?
If it is, then the only option is a repair, and I wouln't be surprised if they didn't cover it under warrantly as it's mechanical damage.
Unless you're feeling brave, and feel like stripping it down and soldering. Although that's probably not the best ides on a 4-month old phone.