使用非聚集索引时，我的SQL查询花费的时间太长

I have a database table that hold customer details and when they call in we use their telephone to lookup their details, but this usually takes about 2-3 seconds but recently it has been taking 5 seconds with no extra data. If I query the table using the home_phone_no = '441903354676' this returns in sub second. But if it is queried using home_phone_no = '441903354676' or business_phone_no = '441903354676' then this takes 5 seconds.I have a database table that hold customer deta