Faulty BMX sold

I bought a BMX from the shop and have already returned it twice for repairs under warranty, the shop is not at fault its their mongoose supplier. It seems as though i have unluckily been sold a bmx that has many problems and keeps breaking, i have broken 3 chains as well as the rear wheel hub and the the front one is not far from breaking as well. I dont have the time or the patience to keep returning and complaining about this faulty bmx and would really appreciate it if the mongoose suppliers would do something about it.