If that doesn't work, I would try concatenating the telephone number field to a character to convert to text (do this in the SQL itself). You'd need to process it after import if you wanted to remove the character.
I'm not sure of the driver (ODBC or OLEDB) that you're using so the following may not work:
SELECT 'A' + [TelNoField] FROM Table
etc etc. If you can, I would go for a concatenation using the sigle quote ' character as it will hopefully be placed into the cells as a textual number requiring no further modification.