Upgrades

When we want to upgrade from Telkom internet from a 2MB line to 10MB line my husband got asked all his details to verify that he is indeed the account holder. When asked his ID number, it was correct, but when the date of birth was given to the operator, the operator said it is not the same as on the system and as a result of that they cut the call immediately. Please explain to me, how can the ID number be correct, but they have a different date of birth... Pathetic in our eyes!!