My LG Optimus P970 won't charge anymore. I've tried different chargers and different batteries. It used to only charge if I held kept the cord at a certain spot/angle in the USB port, but now it doesn't work at all. How much does it cost to fix this?
Is your phone still under warranty? Have you called customer service and asked about it?
If it's not under warranty, then the cost to buy a micro usb jack, the correct one that is, is gonna be less than 10 dollars at a parts store. Sounds like the jack is loose.
The cost however, to have it resoldered onto the main board of your phone including disassembly and reassembly, will be the most expensive. My local repair guy charges about $40 an hour. I have to say, if you've never done any light electronics repair, or soldered anything, that you probably shouldn't attempt to take it apart yourself, as there are many delicate parts that can snap or get damaged if you're not careful.
Another option that i've seen used, is to remove the battery and charge it with a universal charger that either plugs into regular wall outlet or usb jack in computer.
I have one of these and it works on almost any small lithium battery found in cellphones and cameras.
The issue you described is consideted physical damage and will not be covered. It's caused usually by playing with your phone while it's plugged in and it stresses the micro USB port until it snaps off the main circuit board. Chances are it will be cheaper to buy a new phone than it will to send it away and fix it.