bad service

i bought 10 ballons on 26/02/2016 by the time i got to car 2 had burst ,so they replaced it,i then told the lady the ballons were blown to hard she said no its fine. i then got to my shop about 10 mins away in landowne so i hang the ballons on the cars which i had on display, within 15 mins all the ballons had burst, so i called to say what happened. so i went into the store yesterday 1/3/2016 and asked the same lady to replaced 6 of the ballons for me which she refused to do, i then ask her her for the head office number, i called there and spoke to a lady which said she would get right back to me cause the manager was with her, she didnt get back to me , i then called her this morning and she said to me , well they sell 500 ballons a month and i am the only complaning so i put the phone down, i have been buying there for years so are they willing to loose a customer over a 100 rand ?