c-zero died

hi, I purchased a 3 year old c zero for my wife on 15th Feb 16 , 10450miles on the clock since then she has only done approx 20 miles per week, sh does not charge the battery until it shows less than 10 miles remaining on the charge. this indicator over the year has fallen from 66 miles to 47 miles on full charge. last may the car died and was taken to the garage they had it off the road 3 weeks and said it was a loose connection. 3 weeks ago the car died again and went into the garage at first they said she was'nt using it enough and now they say the ac is backing up and causing a fault (whatever that means) and they have asked for 3600 pounds to repair it, the car is only 16 days over the warranty. any advice on my next step they are unwilling to give a goodwill gesture, anybody got the address of the complaints department.