I don't have advice for iPhones, but for service I'd suggest checking out Visible.com. It is Verizon service, but there is no store, everything is done online. Unlimited talk, text, and data, for $40/month. There ate no different plans its just the standard Verizon service.
Everyone has separate billing, but if people.join your "party," or you join someone else's "party" everyone in the party gets a discount on service. $5 off for each person, down to $25/month. If someone leaves a "party" nothing changes as long as their are.still enough people to the max discount. If your party dips below 4 total people, then your bill starts to go back up, but still its $40 max even if you're solo.
The other members of your party don't get any info about you, so people.go on social media and find large parties to get the maximum discount.
My wife and I had Verizon for well over a decade. We switched to Visible a few months ago, and are saving a ton of money.