Broken/faulty audio/mic jack?

I'm so sick and tired of the pc I have. It's a pc that costs almost £1000 and i feel like i've been scammed badly for it. The audio jacks are faulty on EVERY port in the pc. They used to work fine near to when I first purchased it. At the front panel of my pc I plug in a splitter for my headset and the audio split works most of the time but has to be twisted within the port to work fine but on the other hand the microphone barely ever works and has to be twisted for sometimes hours to get it to work for a few minutes, and the slightest movement within that time will cause it to turn off. The mic quality when it is working is also poor and you can hear a fair amount of static. The things i know are:

*It's not the splitter because I've used multiple different aux jacks and splitters and the result remains the same

*It's something to do with the PC but I haven't got a clue how to fix it

How much would it cost to get this repaired? If there are any other solutions I'd love to know. thanks