"Burner phone" is a colloquium used in the United States referring to limited use prepaid phone, separate from your main phone, that's not tied to your identity. Usually used for drug deals or other criminal behavior.
This isn't really a burner phone as the Twilio link I clicked asked me for a bunch of personal information first.
It's a common thing in US spy/criminal movies. Basically a throwaway phone number not tied to you that you might give to an informant or use in some other way to stay anonymous.
but in this case it is probably tied back to you ... (the credit card used to pay Twilio...) So it is not really a burner phone in the traditional sense
This isn't really a burner phone as the Twilio link I clicked asked me for a bunch of personal information first.