NHTSA Complaint #11700450 — 2015 KIA SOUL

I am getting a code that indicates an issue with the catalytic converter. P0420 to be specific. The engine is continually misfiring and check engine light comes on and off randomly. Car broke down completely at one point in October and had to replace the battery but check engine light was still on when I got it to start. The car shakes uncontrollably every time I drive it and gets even worse when idling. I took it to a mechanic and they believe it to be amongst the 2011-2016 SC176 recalled Kia Souls where high exhaust temperatures can damage the engine’s catalytic converter. Have attempted to take it for repairs/open recall and the manufacturers have consistently refused. Help in getting this issue sorted out would be much appreciated.