Merge or combine CF7 Fields

I need combine severa fields tag to create another hidden field to use for osticket cf7 connector, mailchimp connector and CF7 DB

i ask in the form for phone number but i need combine with country code.

it doesn′t work, but i need something similar to:

[text phone-withouth-country-code]

[hidden phone default: value “+34” & [phone-withouth-country-code]]

And use [phone] in mails, cf7 DB, etc