is "%LIKE%" faster than executing multiple queries?
This is bad - it is a table scan  

LIKE %1234


But thousands of rows is not much  

Best would be to have second table with phone 

phone:  
userID PK FK to user   
number PK



select * 
from user 
join phone 
       on phone.userID = user.userid 
      and phone.numer = '1234' 


if you don't want to fix the data design then two column with = will be faster