Seems like there's not much point for me to contact microsoft support.
Same issue with my Surface Pro 4. Bought it in 2017 so can't use the 3 year replacement scheme. Battery has overheated and is bulging. Screen has deformed so much that my type cover doesn't close properly. Took it to the local computer repair store and the guy said it's a fire hazard.
By all means take this up with Microsoft. They are passing this issue up as a customer missuse problem, whereas there have been a number of software updates which were meant to fix the problem of overcharging the battery, which simply did not work. Its a huge design flaw, which Microsoft need to be made accountable. Depending on where you live there may be an opportunity to join a class action against Microsoft peddling unsafe, and unfit for purpose computer equipment. They are currently selling units all across the surface range which may have the same design flaws, ie. unserviceable sealed lithium balleries which are not designed for desktop replacement, however these are being currently marketed by Microsoft for that very purpose. As these units are prone to this fault of overheating batteries, they should be banned by all major airlines as an item that is not fit to be used while travelling on airplanes, whether for business or for personal travel. There have benn many other large corporations that have acted ethically, and withdrawn or recalled their faulty products before someone gets hurt due to hightened risk of exploding battery. I can see the headlines now, when a planes flightplan has been compromised due to a battery incident while inflight. And still Microsoft think that they are above the law, in ignoring the cries for help from their loyal customer base.
******** DO NOT EVER BUY MICROSOFT HARDWARE AGAIN, EVER *******
Spread the word....