Microphone cuts in and out when using Zoom - tech support unable to help. HELP

I bought my XPS13 last month for work which I will largely be doing over Zoom as I'm WFH for the forseeable. When I use Zoom other users can barely hear me, my voice is very quiet and cuts in and out throughout the call. 

I've checked the mic and it works fine, installed all the latest updates and drivers, and performed a hardware diagnostics check. I've spoken to Dell tech support and they can't help, and say if it's a software issue rather than a hardware issue my warranty is invalid. 

I spent a lot of money on this machine and can't currently use it for the main chunk of my work. I wanted to splash out on a top of the range laptop to avoid these kind of issues, I'm not good at tech-speak and when I search online it seems like a lot of Dell users are having the same problem but I have no idea how to fix it. Argh. Please somebody help me.