Most VoIP providers let you use any number as the caller ID with a simple SMS verification. So, if you were to have access to someone's phone for a few minutes

Most VoIP providers let you use any number as the caller ID with a simple SMS verification. So, if you were to have access to someone's phone for a few minutes you could possibly verify it and use the number for making calls and sending text messages from the VoIP service. I believe the SMS verification is something that companies use to avoid liability alone, technically they can use any number as the caller ID if they choose to.