Sony Ericsson - I am not satisfied with the product and service

I bought a brand new Sony Ericsson C903 on 17th May, 2010, sealed box with warranty. Right since day one, there were problems with volume and calls. Slowly the problems increased. In just two months, the keys became hard, phone began to hang very often, speakers went for a toss and even the music player would just skip tracks. I submitted the phone to the service centre at Platinum Mall, Ghatkopar, Mumbai on 27th July, 2010. They told me to come and collect it in a week. But when I went after a week, they said the problems are very major and serious and it will take another week. When I contacted them again after another week, the lady on the phone told me it will take a minimum of two more weeks, they cannot guarantee! All the keys are not working and even the joystick is damaged and they don't have any parts! I don't know what to do! I'm a professional and this is impacting my work. My backup phone is also not in a proper functioning condition (the reason I bought a new phone in the first place) and the repairs are too expensive. I really don't now what to do or whom to contact. I'll never recommend this brand to anyone nor buy it in the future. This is the worst service I've ever come across