Xbox Series 2 Controller Repair - How do I get Microsoft to ACTUALLY sort my problem?

Here's a run-down of the issues I have had, and the process by which I have tried to get this sorted.

1. The controller that shipped with my Series X developed a fault with the LB button where it snapped at the hinge, and wouldn't press down properly or provide any tactile feedback. I submitted a warranty repair request, sent it off with a prepaid shipping label (and that's it), and received a brand new controller in it's place.
   
2. The new controller developed the same issue within a month. Not only that, but the A/Y buttons were also inconsistent in their feel and registering presses. I created a new warranty request, but this time it was a different label to a different address and said I needed to include customs forms. I put these inside the box, only for the package to be returned by UPS after 2 weeks stating there were none. Sure enough, they were no longer inside the box. I attached 3 to the outside as well as inside, sent it again and received a replacement after 3 weeks. The reason for the delay, as stated on the tracking, was that UPS initiated contact with Microsoft to obtain clearance information for 4 DAYS in a row, before finally getting a response.
   
3. The replacement controller was not new - it came wrapped in bubble wrap, without any packaging (which I'd included in the previous return). Not only that, but OUT OF THE BOX neither the A or Y buttons worked correctly, and barely ever registered a press unless pushed with a heavy thumb. Once again, I initiated a return via the warranty portal, attached the documents etc. and shipped it off AGAIN.
   
   However, this time, after 2 weeks of "initiated contact with sender (microsoft) to obtain clearance information" coming up on the tracking for the return parcel, nothing happened. I put in a claim with UPS for a "lost" parcel, which took 2 weeks to clear up, and Microsoft finally initiated a return once the claim was accepted.
   
   Once again, the item I received was a refurbishment wrapped in bubble wrap, and OUT OF THE BOX the left stick is grinding! It doesn't return to centre when let go, and feels horrible to use.
   

I am now on my FOURTH controller, which has the left-stick problem, and I'll be damned if I'm going to accept the same shoddy service and go through the process all over again, only to be given a controller which is broken in some other way.

I need to speak with an actual person at Microsoft, but not only is their Virtual Agent a waste of space, the "Call me back" feature DOES NOT WORK for my number. I have no idea why, but when I use my girlfriend's number to request a call-back, it goes through with no issue...

Their UK call centre number, 0344 800 2400, gives absolutely no way to request a call-back or to navigate through to a representative.

How on earth do you actually get proper customer service from this company?

I NEED A CONTROLLER TO USE MY DAMN CONSOLE!

:)