Here's how you would say the numbers if you really want people to get it. This is how the Army taught me and also this info is from ArmyStudyGuide.com
you would also say it like this slowly as Mike has described above.

Numeral Spoken As
0 ZE RO
1 WUN
2 TOO
3 TREE
4 FOW ER
5 FIFE
6 SIX
7 SEV EN
8 AIT
9 NIN ER