After years, I'm done with Takealot

I bought a airsoft pistol from Takelot, it uses small little 12gram C02 canisters. When I got the pistol I inserted the canisters and used the pistol. Upon usage I notice the the pallets sometimes falls out or that the safety doesn't always work. The muzzle on the block and slide was also very lose so it was obvious that the gun would not last. I returned it and they Takealot complained that the gun could not be returned without the C02 canisters. They provided 20 and I used 2 for testing. There is no other way to test the gun without using the C02. I advised then that I chucked the empty canisters in the bin and returned the rest of the items. I also advised that I am more than happy to pay for the used canisters. They retail for about 10 - 20 rand each and the pistol is 3000 rand. Now they want to send back the defective pistol of R3000 and the more I try to explain things to them or the more I ask for a manger or supervisor the more they just ignore me. I would just like a refund.