Massimo Dutti — exchange defective item

I have a bought a t-shirt and after washing it 2 times, I found it shrink about 2 cm length, and when i went to the store to replace it they said that we will send a complain to administration and we will respond within 72 hours then no response came so i visited them 3 days later they told me that my complain has been rejected and we can't do anything to you.