A full PRI (in the US) can maintain 23 calls , all calls are processed in the d-channel, but the treatment of any prioritization is only available to the povider, and they really don’t want to do that, further, if their equipment is overloaded by 1000 calls at 8:01am it impacts the way their equipment handles both your calls and your peers calls, they are obliged to return to the caller a response and are generally not particullary caring todo your prioritizations on an ad-hoc fashion defined by you. the toll-free solution moves the onus to the “resp-org” and the contract they have with you, toll-free numbers are “virtual” they can only be forwarded to a PSTN number for termination, and yes it is possible they are the provider of the PSTN number also, That is why the cost more and are better for broadcast situations that as you see can be very “spiky”