On POTS caller ID is there in the central office frame for billing purposes, but sending it to the customer side is a simple bit flip in the configuration for the port in the card in the frame. Was generally here turned off unless you paid for the service, but the cellular providers turn it on for prepaid so that they get return calls off the prepaid service, otherwise no calls unless you leave a voice message, and most owners on prepaid will not call back to unknown numbers, or reply at all to no number calls. postpaid (contract) numbers they charge a fee as part of the monthly subscription cost, which is just a money making thing for them, the $1 per bill is just extra profit off the business customer, who in any case is paying off the inflated handset price anyway over a 24 or 36 month period. They just get some sop of free minutes, a small data bundle or a certain number of SMS sendings, that is almost always going to be used anyway. No operator these days here offer unlimited calls or data, though there are some grandfathered plans where you get actual value if you have a massive call volume or data use, but they do not offer that to those who can use it.