Broken plastic cups

I purchased plastic cups from Tupperware and within a month one broke and I threw it away the next week another one broke again and my colleague said I must send it back as Tupperware is not suppose to break. I told the lady bout the cups then she said I must bring the cups back,I told her that I threw away the other cup then she said she can't take them back since they short and Tupperware won't accept it. I thought tupperware is quality but for a plastic to break I'm even more disappointed and I still need to pay the full amount.