I suspect that most people, no matter how well they speak a foreign language, find it difficult to deal with numbers in other than their native tongue. I’ve noticed many times that someone has asked me to give them numbers in their own language, “because it’s easier.” I’m no different: if I have to write down a phone number, I prefer to have it recited to me in English.
For starters, Italians have a completely different way of speaking numbers than Americans. Suppose you were reciting out loud the (fictitious) Washington phone number: (202) 123 4567. Most Americans would say: “two oh two, one two three, four five six seven.” Many Italians would say the Italian equivalent of: “Two hundred two, one hundred twenty-three, forty five, sixty seven.” Or, even more confusingly, they will break up the seven-digit number differently than Americans do and come out with: “Two hundred two, twelve, thirty four, five hundred sixty seven.”
Americans do use hundreds and thousands in phone numbers where they are round numbers, e.g. a toll-free number might be given as “one eight hundred four five five three thousand.”
Saying hundreds (never thousands) is more efficient in Italian than English, because the Italian for hundred is “cento”, and you don’t need to say “one” when there’s only one hundred. So “cento ventisette” (127) is quicker to say than “one hundred and twenty seven.” (Yes, we were all taught in grammar school that saying “one hundred AND…” is wrong, but many of us still do it.)
On the other hand, if someone starts saying “cento…” my instinct is to immediately write 100, before I hear that the tens and units columns are also occupied.
What about other kinds of numbers? Take years: the year 1956 is read by English-speakers as “nineteen fifty six” or, if you’re old-fashioned, “nineteen hundred and fifty six.” An Italian would say “mille novecento cinquantasei” (one thousand nine hundred fifty six) – twice as many syllables.
And then there’s the matter of dates. Americans write and say “April 25th, 2005,” or 4/25/05. Italians write and say “25 Aprile 2005” (venticinque aprile, due mila cinque – note that there’s no ordinal: it’s twenty-five, not 25th) or 25/4/05. Most of the rest of the world also abbreviates dates in the day/month/year format. Having lived all over the world, I can never remember which style is used where, so I’m always messing up forms that require me to fill in a date.