here's how i started tackling it: strip everything out, and then format depending on 10 or 11 digit lengths.

I think i'd remove letters and replace with their corresponding numbers...

I'm ignoring inserting periods before and after words in the phone;

/*

HowsThis

866.611.3847

800.2KM.IDAR

800.001.4015

800.001.4015

866.231.2244

888.401.KOND1

855.EZP.8107

1.855.OKR.8107

1.800.228.2244

1.800.483.SAVE(7283)

800.228.2244

666.606.0399

*/

IF OBJECT_ID('tempdb.[dbo].[#myphone]') IS NOT NULL

DROP TABLE [dbo].[#myphone]

create table #myphone (phno varchar(20))

Insert into #myphone values ('(866) 611-3847')

Insert into #myphone values ('(800) 2-KMIDAR')

Insert into #myphone values ('(800)-001-4015')

Insert into #myphone values ('(800)001-4015')

Insert into #myphone values ('(866) 231-2244')

Insert into #myphone values ('(888) 401-KOND1')

Insert into #myphone values (' (855) EZP-8107')

Insert into #myphone values ('1 (855) OKR-8107')

Insert into #myphone values ('1-800-228-2244')

Insert into #myphone values ('1-800-483-SAVE(7283)')

Insert into #myphone values ('800 228 2244')

Insert into #myphone values ('666 - 606 - 0399')

SELECT * FROM #myphone

CROSS APPLY(SELECT REPLACE(REPLACE(REPLACE(

phno,'.',''), --dots

'-',''), --dashes

' ','') --whitespace

As FirstPass) AS SimpleClean

CROSS APPLY(SELECT LEFT(FirstPass,6) As Section,

RIGHT(FirstPass,LEN(FirstPass) -6) As RearSection,

REPLACE(REPLACE(LEFT(FirstPass,6),'(',''),')','') + RIGHT(FirstPass,LEN(FirstPass) -6 ) As ReplacedSection) AS Parens

CROSS APPLY(SELECT CASE

WHEN LEFT(ReplacedSection,1)='1'

THEN STUFF(STUFF(STUFF(ReplacedSection,2,0,'.'),6,0,'.'),10,0,'.')

ELSE STUFF(STUFF(ReplacedSection,4,0,'.'),8,0,'.')

END AS HowsThis) AS LowellsVersion