I personally think that 'new number' should be accepted as would 'new phone number'.
Number = رقم
Phone number = رقم ہاتف
I agree with GvdMvzik_; over time, it has become understood that we are referring to a phone number when we say this
"Mike" sounds like Malik, but no near as Mike!
How would you say "Is your phone number new, Mike?"