Unless the company specialized in sales outside the UK and likely also outside the EU, I think this company is probably breaking the law, as are the carriers using their services. I doubt the people who buy phones on extended credit will have the cash laying around to bring up a lawsuit, though.
https://ee.co.uk/content/dam/ee-help/help-pdfs/pay-monthly-n...
Section 10 explains ownership:
Starting with...Section 10.1:
"You may get Equipment from Us directly when You take out a Price Plan, whether for free or for an upfront cost. Unless We tell You otherwise, or You get Equipment under a Finance Agreement, We will own any Equipment provided to You by Us for the first six months of the Minimum Term."
...and it goes on.
But yet they all make pains to separate airtime, and devices in the contract for example clauses that say you can't cancel the airtime contract if the phone proves faulty
Just like if I go to a bank, get a loan for a car, buy that car, and stop making payments... THE BANK OWNS THE CAR.