Can't fulfil warranty

So I have an LG Velvet phone. The charging port went funny a few weeks ago, and the phone only charges of the charger is plugged in one direction and not the other. The Hdmi output stopped working properly same time, and the battery started draining like crazy.

I called customer service and they said phone was under warranty, so I went in and they said they'd sort it all. Parts will take 6 weeks to arrive. I'm going overseas though, and need to have a battery that lasts. They said they won't cover it u der warranty unless I get everything done at the same time, so I have to fork out for the battery. Battery itself costs R438, which I'm willing to pay, but then they want R550 to install. So I total they want a thousand rand when I shouldn't be paying anything. This just isn't right, especially when the phone is still under warranty.