I support a more broad approach: a public body whose inside will be jailed for life if discovered taking payments from third parties, with enough tech to appear generic Citizens to the corporate surveillance, with funds to buy things regularly, and get donated to poor thereafter.
If they found anti-user practice they have sanctioning power in the order of % of revenues, little the first time, hard the second, claiming personal executives responsibility a third breach. They not only check products but also services, software and hybrid stuff.
Selling crap is subject to little sanctions, like if you sell thing that are clearly designed to break in very little time, you sell things to elicit more money forcing mandatory services etc you'll pay so much that's simply illogical trying to.
Imposing just a phone number and a reachable human on the company side I fear is far from sufficient: these days is common arrive to a humans, but a powerless one, who can just open or "bump" a ticket. Again simple laws who take into account only one side fail for easy corruption, that's why a public and transparent, forced to be independent and only able to operate to a certain extent actor is needed. Most people is honest in a society because that's the best evolution behavior but most if far from all, so rules must be crafted on humans defects making bad behaviors disadvantageous from all side possible. It's hard, of course, but not impossible, and a real Democracy can control and block dangerous derives quick enough.