The payment network charges the bank a very small transaction fee for using the network, but net they are essentially letting the bank make the most from the interchange fee, hence the banks are on the subsidy side.

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The cards will deduct the purchase from a customer's checking account, but skirt the interchange-fee network.

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Shortly after, TV Azteca said it wouldn't allow Mr. Slim's companies to advertise on its network until Telcel lowered the interconnection fee that it charges rivals to connect to its network.

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