Wonder if they've blocked the providers of temporary virtual phone numbers?
I suspect if there would be enough demand for this service, a "grey" industry of people buying prepaid SIMs and renting access to them would appear.
This assumes there is a way to tell which numbers are prepaid or not. To the best of my knowledge they both originate from the same pool of numbers and it is impossible for an outsider to tell whether a given carrier's number is prepaid or postpaid.