If this is the case, and as @Someone1234 recalls the UK used to have zero rating services (I honestly don't remember them), what changed in that landscape to br

If this is the case, and as @Someone1234 recalls the UK used to have zero rating services (I honestly don't remember them), what changed in that landscape to bring data prices to significantly lower points? Surely not just competition on its own. The US mobile market isn't a monopoly (although I stand to be corrected if this is spoken in ignorance).