Did not replace my breaks when I requested

I took my car in for service 3 months ago and advised my brakes needed to be replaced. The car came back and I was advised everything is fine and I do not need to replace my brakes yet. I continued driving my car since I'm not the expert and the sound went away or wasn't too bad... The second I get another warning from the car stating I need to check injection I started panicking cause the sound suddenly started getting worse then I take in and then get slapped with the largest bill. I was so disappointed in renault and I don't know if Its because I am female or what but not the damage of the brakes had now caused more damage to the car... This is so not fair especially since I've only owned the Carr for just over a year and it hasn't even done 30000km ever