Swollen battery. Iphone ruined

My I phone 6S was still in mint condition after 22 months of use. I took it to Istore Clearwater to have the tired battery replaced in May 2019. In October 2019 I e-mailed them to inform them that this new battery was failing and the phone was shutting down. They informed me batteries are only guaranteed for 90 days. By November the phone would not switch on anymore, so I placed the phone into its original box and went out and bought a new Iphone. On taking my old Iphone out the box a week ago to go and have it repaired again, the battery had swelled up 10 fold thus breaking the phone in two halves, completely destroying it. Apple thus has effectively installed a defective part into my phone, completely destroyed it and have now quoted me R2000.00 to repair or replace it.