Walmart is pressuring Amazon's fulfillment business, Wells Fargo analysts wrote on Monday.George Frey/AFP via Getty ImagesWalmart's logistics business is pressuring Amazon's own, according to Wells Fargo analysts.Walmart is offering a cheaper version of Fulfillment by Amazon, which could limit Amazon fees.Wells Fargo cut its rating on Amazon to equal weight from overweightAmazon's fulfillment business is feeling the pinch from another major retailer: Walmart.The big-box chain has spent years building its own logistics network.