Bad service from we rent a car company

On the 29 May I have signed a rental contract with We Rent Cars through bryston executive cars. I day after the car did not want to start and I reported that, it was discovered that the battery is dead since it was fitted in 2016. The promised to fit a new battery but till todate they never replace the battery. The one I am currently using I had to borry it to a friend. It's very disappointing. I was never even given the copy of the contract. Can I please be assisted