One way to clean up and reformat telephone numbers is to strip out all extraneous characters, then apply Excel's built-in telephone number format. This formula above uses a series of nested SUBSTITUTE functions to strip out spaces, hyphens, periods...
The Excel SUBSTITUTE function replaces text in a given string by matching. For example =SUBSTITUTE("952-455-7865","-","") returns "9524557865"; the dash is stripped. SUBSTITUTE is case-sensitive and does not support wildcards.
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