Hyundai EL did me dirty and i need help because this is my precious first car that I am still paying for 😭😭😭

I took my car for a service on the 26th of Feb, Mind you I hardly use my car because I have a work one I use everyday. Around March I used my car and heard there was a knock kind of sound coming from the left back wheel when driving on an uneven surface. I contacted Hyundai and the said I should bring it in when I asked about warranty. They checked the car and said all is good and everything was tightened. They said I could contact them when it's still there. I didn't hear anything because EL road I use doesn't have never surfaces or speed humps until I got to Mthatha where I heard the sound when going over a hump. I contacted then and nothing