The mystery person who contacted Charles Croes about his Cell Phone Rental service was most likely the undercover US DEA Agent that was on the island and who hooked up with the chaperone that stayed behind after Natalee was discovered missing. We know that a undercover DEA agent help out greatly during the first few days of this case.
So Croes met with this person for further discussion? But did not reveal the content of their conversation? Thanks again!