That's because GB didn't sell the gun to you, a dealer or individual did.
Have you contacted the seller? What type of issue are you having with the firearm? Have you checked with a local gunsmith to see if there's an actual problem with the gun, or if it's perhaps operator error?
Every time I've purchased a gun through GB, they've sent me an email trying to get me to buy a "protection plan" type warranty. I'm guessing you declined purchasing that? Kinda like buying a used car, declining the extended warranty, then wanting the dealer to fix or take back your car when it tears up.