Game ******* and poor customer treatment

So I bought a Little one three wheeled pram last year July when I was pregnant as part of baby preparations. When baby arrived and we started using it, we quickly realized that the back wheel kept coming out. We stopped using it for a while and in March decided to return it for a functional one. Unfortunately we had lost our slip. After weeks and weeks of waiting for feedback they called us to tell us they found our slip. When we got to the store instead of exchanging it they gave us a voucher for less money than the value of our pram so now we cannot get the pram anymore yet we brought back THEIR product for being defective. We didn’t want money We wanted an exchange. My baby still has no pram when we go to church. I It’s painful.