Substandard battery replacement swells and damages iPhone 6s

Had an iPhone 6s battery replaced just over 6 months ago through weFix, and this week, in a matter of a few hours, it started swelling, damaging the phone to the point of it being useless. I would highly recommend that any battery repairs rather be done through an iStore, where some sort of guarantee can be given on the parts, rather than the substandard batteries used by weFix. When contacted for advice, I was informed that the warranty weFix offers on batteries is 3 months.