varchar
Even though for a phone number you primarily use integers, there is any array of other characters that can be used such as (, ), [, ], -, and +. Therefore what you're storing is a string. What better datatype to use than a string
varchar. Now, you could use char, but that entales padding... not a problem if you practice good coding habits and TRIM everything all the time anyway. And anything like a memo/text field is OVERKILL... and with MSSQL there are even datatypes such as nvarchar... again, overkill. varchar is usually sufficient.
