How can I say telephone number ?

One of my classmate told that she was confused with taking a note other's telephone number.
somebody informed his number, saying " four ones (or one)". It meant "1111".
ONe day I asked an american lady about it, and she said that the way of telling phone number was not right. The reason is that it can be confused with "four one", and it can be "411" that is telephone information number. She told me when I tell phone number to others, It is improtant to speak clearly. nothing is needed to inform. If same numbers are beside each other, we can say " double --". For example, 3348 can be "double three four eight".