Different numbers will be changed properly only if they are placed in different columns of the CSV file. If a contact has two or three numbers separated by commas and written in the same cell, the converter will not figure out how to allocate them to different vCard fields. I ran into trouble with this while my contacts were being exported from an old Android phone because a great number of the entries had combined numbers. I divided them into columns such as Mobile, Home, and Work before doing the CSV to VCF conversion. A good CSV to VCF converter will recognize these columns and map them correctly. I tested GainTools once, and it did a great job with that. The conversion from multi-number contacts to vCard is very accurate when the CSV file is clearly organized.