By your logic, virtually every single business owner on the planet would be guilty of whatever you're accusing the Walmart execs of. Cars, computers, paper, pens, phones, wire, etc etc etc. There are very few popular products or services that don't facilitate criminal/antisocial behavior in some capacity.
But there are important differences between scam calls and money transfer. The most obvious one is that big mobile companies don't profit significantly from scam calls. Another is that the big mobile companies are working quite aggressively to keep dubious callers off their networks.
Consider, on the other hand, that assorted fly-by-night telecoms providers are scammer-friendly, in the same way that a small number of network providers are friendly to spam, child porn, and other criminal activity. Those people are, in the FTC's phrasing, turning a blind eye. I'd be fine with that being made illegal in the same way it's illegal to fence stolen goods.