A B C D E f G H I L N O P Q R S T u V W X
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The one from the caller (A participant) the called party (B participant) to display phone number (clip) is checked for validity by the TC provider using screening. If a TC service provider, such as a call center, receives permission from its customer to signal the customer's own number for outgoing calls, the call center operator must use this number for his own SIP Trunk with appropriate proof of his network operator get validated.