disappointed in bulb life

Good day

Purchased a Magneto rechargeable LED lantern - no i dont have slip or box, becuase i really didint think that i was buying a product that would let me down.

Product does not charge, I have ensured that its plugged in - when needed that light lasts about 4 min and then dims and then goes off after about 5 min.

i have 2 of the smaller units and i am truly impressed with the battery life and strength of the bulb - hence i bought the bigger unit - very disappointed. Is there a way that i can get it replaced?

Anita Painter ***