A method is provided for supplying service to mobile stations (MS) (20)
utilizing a wireless telecommunications network (A). Each of the MS has a
home country and a home network and is programmed with an identifier
comprising a number including a set of digits. Each identifier is one of
two types including a first type of identifier that uniquely identifies
its MS globally via the entire set of digits making up the identifier
(e.g., a true International Mobile Station Identity (IMSI)) and a second
type of identifier that uniquely identifies its MS within its home
country via a subset of least significant digits making up the identifier
(e.g., a Mobile Identification Number (MIN)-based IMSI). The method
includes: obtaining the identifiers from MS entering the wireless
telecommunications network during a study period; collecting a subset of
most significant digits from each identifier obtained during the study
period; compiling a list of digit patterns, each digit pattern in the
list corresponding to one of the subsets of most significant digits
collected; receiving identifiers from MS accessing the wireless
telecommunications network; and, comparing the subsets of most
significant digits of the received identifiers to the compiled list to
determine which of the received identifiers are the first type and which
are the second type of identifier.