If it happens when you are clicking on a number, then what you are experiencing is an "Apple safety measure". Many people, not us of course
, accidentally tap on things like phone numbers. If the number was immediately dialed, then the person would need to cancel the call and the recipient might see that they received a call but the person hung up; they might feel the need to call back or end up in a deep state of wonderment.
So Apple gives you a second chance to decide if you really intended to make the call. Might be comparable to "are you sure you want to delete this item?" in other situations.
