Add a number/numbers to a 'send' group (excluding 'merge' groups).
Arguments:
String groupName:
Name ID of the group to add the numbers to.
String numbersArray:
The MSISDN (mobile number) you wish to add. If you want to add more than one number use a comma-delimited list.
Returns:
An integer with the total of added numbers to the selected group
Specific error codes:
The group ID or name was not specified or was invalid.
A number was not of a valid format.
error code 404 is reported if the group does not exist. See General error codes.