Pathetic service

I went to nandos in grassy park. I asked that I please be given extra sauce. When I went to collect I asked that they through in extra sauce as there was hardly any extra sauce in. They lady Grace told me there is and she cant add more. I showed her that if I tip it over theres no sauce. She insisted that there is extra sauce. I asked for the manager and she said she is the manager. I requested for a refund instead. This is the third time I go to this store and they refuse to give extra sauce. We pay alot of money and then dont get the service asked for. Grace has a very bad attitude. I always buy there but dont think I will ever go back.