NHTSA Complaint #11437441 — 2016 KIA SOUL

My check engine light was continually going on and off for a month took it t get it check found out it was converter and their a recall for converter . Took to the Kia dealership with check engine light on to have this taken care they did only a reboot of the engine and light was off so I thought the problem was solve bit the very next day the light was back on went again to the check engine light and again they said it was the catalyst converter took it back to dealership and told their was no more recall on my vehicle I told them about the problem and recall they didn't fix and was told it cost me to do diagnostic test and I week to do that I told I can't be with out a car that long so it was nothing they can do I left and now my check engine light coming on more frequently I might have this fix myself I don't want more engine or worst but why should I pay when this was be taken of them I received a recall notice for same thing 2 days ago and they still won't fix it free of charge what going on and now what shall I do?