i need to check the first 3/5 character of string mobile number. having the above mention thing, if so need to extaract after that number to last number.

Declare @3Code varchar(3),@2Code varchar(2), @1Code varchar(1), @orginalNumber varchar(15);


SELECT TOP 1 @3Code = SUBSTRING(Mobile, 1, 3)
    ,@2Code = SUBSTRING(Mobile, 1, 2)
    ,@1Code = SUBSTRING(Mobile, 1, 1)
    ,@orginalNumber = Mobile
FROM LOGIN

IF (@3Code = '971')
BEGIN
    DECLARE @length INT = 0

    SET @length = (
            SELECT len(@orginalNumber)
            )

    IF (@length > 8)
        SET @orginalNumber = SUBSTRING(@orginalNumber, 4, 10)
    ELSE
        SET @orginalNumber = @orginalNumber
END

IF (@3Code = '00')
BEGIN
    SET @orginalNumber = SUBSTRING(@orginalNumber, 6, 10)
END

IF (@3Code = '000')
BEGIN
    SET @orginalNumber = SUBSTRING(@orginalNumber, 7, 10)
END

IF (@3Code = '+')
BEGIN
    DECLARE @extractNumber VARCHAR(20)

    SET @extractNumber = SUBSTRING(@orginalNumber, 2, 15)

    DECLARE @3CodeEn VARCHAR(3)
        ,@2CodeEn VARCHAR(2)
        ,@1CodeEn VARCHAR(1)

    SET @3CodeEn = SUBSTRING(@extractNumber, 1, 3)
    SET @2CodeEn = SUBSTRING(@extractNumber, 1, 2)
    SET @1CodeEn = SUBSTRING(@extractNumber, 1, 1)

    IF (@3Code = '971')
    BEGIN
        SET @length = (
                SELECT len(@orginalNumber)
                )

        IF (@length > 8)
            SET @orginalNumber = SUBSTRING(@orginalNumber, 4, 10)
        ELSE
            SET @orginalNumber = @orginalNumber
    END

    IF (@3Code = '00')
    BEGIN
        SET @orginalNumber = SUBSTRING(@orginalNumber, 6, 10)
    END

    IF (@3Code = '000')
    BEGIN
        SET @orginalNumber = SUBSTRING(@orginalNumber, 7, 10)
    END
END

Note: the code is too lengthy I need to optimize.