Suzuki Northcliff horror

I am very unimpressed and disappointed with the service that I have received from Suzuki Northcliff. I have a 3 month old car that is suddenly giving me issues with the tank. I previously reported the issue and the technicians could not detect the fault and they assumed it must be the petrol in the tank making the sound I was hearing. About 6 weeks later it started affecting the gauge and the gauge was faulty and was not reflecting the correct amount of petrol left in the tank, this resulted in two incidents where I was stuck with a car that had full bars but no petrol. I managed to have it booked in and assessed thereafter told that it would take 21 days for the part to arrive as it had to be ordered. The dealership is now telling me that I have to wait until mid June for them to fix my car and their recourse is for me to drive a car they have loaned me which is a car that I never intended on buying and is a car that I am not paying for. The loaned car which I am liable for should any damage occur. The car I purchased is a brand new car and so I have asked for an entire replacement or have it repaired timeously as this is a terrible experience.