If I understand your question this should meet the requirement:
SELECT
t2.phone_number
, convert(varchar(10),t2.[date],121) as t2_date
, convert(varchar(10),t1.[date],121) as t1_date
, datediff(DAY,t1.[date], t2.[date]) as diff_dates
FROM table2 AS t2
INNER JOIN table1 AS t1 ON t2.phone_number = t1.phone_number
AND t2.[date] between dateadd(day,-5,t1.[date]) and dateadd(day,5,t1.[date])
see: this sqlfiddle
results from the sample data:
| PHONE_NUMBER | T2_DATE | T1_DATE | DIFF_DATES |
|--------------|------------|------------|------------|
| 10005 | 2013-05-12 | 2013-05-10 | 2 |
| 15555 | 2013-07-19 | 2013-07-17 | 2 |
| 58746 | 2013-09-20 | 2013-09-20 | 0 |