If you have added this phone number as an attribute, you can change the country code by editing the listing.
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You can find this text in Loco Translate > Plugins > HivePress, as shown in the screenshot Awesome Screenshot
If you mean to set up a default country, please navigate to WP Dashboard > Listings > Attributes > Edit current attribute > Default Country, as shown in the screenshot Awesome Screenshot
If you mean to set up a default country, please navigate to WP Dashboard > Listings > Attributes > Edit current attribute > Default Country, as shown in the screenshot Awesome Screenshot