My understanding is that the finite bandwidth of the spectrum puts a limit (for a given level of technology) on the total data capacity of the network, not on the number of service providers. Could we not have more providers for the same number of users by divvying the spectrum into more chunks? Instead, I think the number of providers is limited by the huge entry costs of building towers. It's the low marginal cost of operating these towers (compared to their build costs) which leads to monopolies.

I would love clarification.