disgusted

I have purchased a pram from game store and my baby as only used it around 4 months. During the fourth month I see that it has lost its motion and very wobbly. I have complained to the store manager and he has mention to my husband and I its the baby's weight. What nonsense is that my baby is only 6 kgs I'm very d issappointed as he said we need to live with it and he can't do anything after we showing him how the pram is so unstable . This kind of service for customers is pathetic .