mattmo

I just bought a next shocker mountain bike
when you pedal the bike then stop and just coast it is supposed to freewheel
mine will freewheel for almost a complete rotation of the rear wheel but when the wheel gets in a certain spot of rotation the chain will move and pull on the chain tensioner but then it will go back untill it is in the spot of its rotation when it will move the chain again

I know this is confusing to describe but Does anybody know what is wrong with my bike?

Fable

Could be a problem with the hub, could be a wonky derailluer. Hard to really say from your description. I would just take the bike back and asdk for a refund or exchange. Unfortunately your bike is mass produced using low grade designs and parts. The parts of the parts are a little dodgy as well. I advise returning for refund and heading to a Bike specific shop. One that sells only bikes. An entry level bike there won't be to much more expensive but the quality in parts, workmanship and support are more than worth the price. If you can't afford any more or just don't want to, return it for an exchange. Niggles and naggles are common in department store bikes. For the most part if they are ridden recreationally on an occasional basis they work fine, but stupid breakages or part failures are not at all uncommon. The harder you ride it the more flaws will be exposed. Another reason to purchase a "real" bike. Some fathead will chime in with their story of a wal-mart bike that saw 29 years of constant service and numerous podium wins but that is the exception rather than the rule. Try posting this in the mechanical section as well. I personally would leave out the brand name. There are some different fatheads who must ignore the question asked so they can focus on how Next blows the goat.
Good luck getting this resolved. If all else fails, you can always take the bike to a Bike Shop that will correct the problem for you. This could very easily amount to a large fraction of your initial purchase price. Continuing problems that require service could swiftly rise above the bikes whole purchase price. Another reason to check out the Bike Shop bikes. They often provide service plans of a varying nature.