When exporting (unfortunately you do not specify which tool use) you specify which attributes you want to export. The names of the attributes and their compliance with ADUC GUI Tool can be found in the this article.
You need attributes:
givenName,sn,telephoneNumber,pager,mobile,facsimileTelephoneNumber,ipPhone
But they can be added (hidden under the "other" buttons):
otherHomePhone,otherPager,otherMobile,otherFacsimileTelephoneNumber,otherIpPhone
PowerShell export example to csv:
get-aduser -Filter * -property * | Select givenName,sn,telephoneNumber,pager,mobile,facsimileTelephoneNumber,ipPhone | Export-CSV -Encoding UTF8 phones.csv
CSVDE export example:
csvde -r "(&(objectClass=user)(objectCategory=person))" -l givenName,sn,telephoneNumber,pager,mobile,facsimileTelephoneNumber,ipPhone -f phones.csv