Quality issues

I am very disappointed with the service I got from checkers I brought a bag pack in February 2021 for my child now the stitches are coming off next to the zip I then took the bag to checkers to show them I was told that the bag does not have warranty I called head office explained everything to the consultant he then said I should go back to the store and ask to speak to seun and I went back he took my numbers and said he will call me I received a call from head office to say they spoke to seun he says the bag is damaged due to negligence how can I be negligent by taking off stiches while my son needs that bag he then said I should take the bag to the taller they can't help me