free market forces is great when the is information symmetry between buyer and seller. In that world no person would ever be surprised when the phone bill is sent.

Now the question is, how many consumers knew roaming prices (for places which they would travel to) when they had the opportunity to compare companies and made the decision to enter into contract with a phone company. If the answer is almost everyone then regulation is completely unnecessary. If the answer is almost no one then competition is basically impossible and the consumer just have to hope that the contract they signed several years ago was a good one and not a exploitive one. Regulations in that case reduces risk to the consumer.