"OH" or "0"?

Les always makes fun of me when he hears me giving my telephone number to anyone because I say "5-OH-5-6 ZERO x-x" for 505-60xx (x for privacy issues). I don't know why I say the "OH" and then automatically follow with the "ZERO"! When I give my home telephone number, I always say "ZERO" but there's only ONE "0" in that number!

CLICK HERE to see the Grammarphobia article "The Many Ways To Say Nothing". OH, I guess I'm not the only ONE!