Remove white space and parenthsis from global from entry variable
I haven't tried this but I think that you can use the twig replace function. Something like:

{{ global.phone|replace({"(":"", ")":"", "-":"", " ":""}) }}


Update In your case, since the prefix (1-) is required, and "-" are allowable, the replace string for "(555) 555-5555" would be:

{{ global.phone|replace({"(" : "1-", ") " : "-"}) }}