Given that this bike is just a week old, I would consider returning it, or at least reaching out to GreenZone, as inexpensive parts should not mean defective. Of course, you might want to get it to a mechanic as it may just be an assembly issue... something did not get tightened / adjusted properly. If it is defective, GreenZone would probably send you replacement parts. Also, I wouldn't buy new parts until I was clear about the problem. Is it a BB issue, crank issue, frame issue? (there could even be mis-threading on the cups which would prevent proper adjustment of any BB) - any # of possibilities. Dealing with this warranty issue now will also give you an idea of what GreenZone customer service will be like should you be unlucky enough to have other problems down the road.

I recently bought a Genesis and the rear axle was bent... I contacted the distributer and they were happy to send out a new wheel after I documented the problem. They even volunteered extra headset bearings as the headset was way overtightened and turned in a ratcheting manner. It was a pleasure doing business with their technical support folks. They were polite, forthcoming and accommodating... and seemed genuinely pleased to get my feedback and insights. So before you spend money, I'd get it working as the manufacturer intended before choosing where i want to put my upgrade dollars.