Appalling customer service

I bought my dad a second hand car on 20 December 2019. To this day, I'm still being sent from pillar to post when I make enquiries regarding the spare key that they never gave me. They keep taking my number saying that they will call me back and they never do. They never update me unless I call and the excuses are always useless. I constantly have to follow up with them and its exhausting. I don't know what to do anymore. Horrible service of note.