Need Help With The ALTER Command

Hello everyone,
I just started learning sql and I came across a slight problem.
Assume I have a customer table composed of the following fields:
Customer_Number,Sname,Street,City,Postcode,credit_lim,balance.

What I want to do is to drop the Street,city,and postcode fields and add the following: fax,email,and phone.

Is it possible to use the following command:

Alter table customer
Drop column street,city,postcode

Or should I do as following:

Alter table customer
Drop column street

Alter table customer
Drop column city

Alter table customer
Drop column postcode

And the same goes to adding the phone,fax,and email field.
Thank You.

NB: I need to use the Alter command and nothing else