you're right, I missed that number is set in that loop.

However, we are quite sure we'll get the same details for each phone numbers, so can maybe declare `details` outside of the `for` block and do getContactDetails only if details is undefined. What do you think ?

Another solution is to call getContactDetails on `tels[0]` (of course, checking before that `tels.length` is truthy, maybe in the early return condition at the very start of the function)