By default, this app prepends a 1 to the phone number. If this doesn't work for you, go to manage extensions->click the three dots->options->under "Tel Link Format" delete the "+1" at the beginning of the text box.

Does the job, I encounter mostly ZA formatted numbers, was cable to customize the link to tel:{0} which removed the US (+1) dialing code.

Looks good for 0.4.4 release.

Works fine with asterisk.