Country Table Lookup

Was wondering what logic can be used to lookup what country sms is being sent to..

Hope u can help me out..  its something that is done usually by providers.. and i need to implement this logic..

Wish to find a way to be able to tell from a International mobile number i.e +8684444xxxx
that this number is a gsm in xyz country.

Then I will be able to add a charge my clients based on the numbers and country of destination since each country is different to send sms.. in terms of charges..   when I have picked the country code that sms has been sent to.. I can deduct then the sms credits from that account..

How or what algorith or logic can i use for this..

If all the country codes would be similar to +30 and +40, it would be easy. But some countries
 have 3 digits, and for some, the first 2 digits are identical to a country with 2 digits. For instance:
Spain - 34
U.S. Virgin Islands - 340

China - 86
Trinidad and Tobago - 868
St Kitts and Nevis - 869


hmmm  how or do u have any methods how I can approach this.??

much appreciate any info or docs.
:)

/george