About a month ago, Verizon and Walmart together launched Walmart exclusive Verizon Prepaid plans. At launch those plans came with 5 GB of data for $50/month and 10 GB for $70/month. Both plans also included unlimited talk, text and international text with data carryover for one billing cycle. The $70 plan also included international calling to Mexico and Canada.
Since Verizon launched those prepaid plans at Walmart, it has added new prepaid plans of its own to its standard lineup that are identical to what it was selling at Walmart.
Just a few days ago a reddit poster noted that Verizon and Walmart have increased the amount of data included with the Walmart exclusive prepaid plans. The $50 plan now includes 7 GB of data and the $70 plan now offers 12 GB of data. The plans retain the other features that they were originally launched with such as data carryover, and international talk ($70 plan only) and text.
I'm not exactly sure and can only speculate as to why Verizon is offering a better deal to Walmart customers than what you can get directly from the carrier itself. It is possible that Verizon is using Walmart as a test bed to try out new plans, or perhaps the carrier wants to offload its prepaid plans to Walmart. One thing that is for sure is that at the moment the plans are not being advertised on Walmart's website. It appears that they can only be purchased in store.