Samsung A3

I currently own a Galaxy Note 4. After only good experiences with Samsung I decided to purchase my girlfriend a Galaxy A3. After only 3 weeks the screen started developing hairline cracks (barely visible but enough to be annoying) The service I've gotten from both the outlet store I bought from and samsung is appalling. I was told all Samsung phones are covered by one of the 3 ADH packages as is my note4 (Apparently not the case) I have damaged screens before but have never had this happen. The cracks are due to a manufacturing fault and not due to external damage and/or accidental damage and I would insist that it be repaired! The quotes to PAY to have it fixed amounted to between 25% and 30% of the value of a new phone!!?? Ive been told by staff that I am **** etc. Pathetic service!! If this isn't resolved I will definitely make sure everyone I know will stay away from Samsung midrange phones.