Phone numbers not being registered in Brevo contacts

Greetings,

We’re using the integration between Contact Form 7 and Brevo. The names and e-mails are automatically created in our contact list in Brevo, and they are integrated in the selected lists.
Nevertheless, the phone numbers aren’t registered in Brevo. The field appears empty in the created contact.
I’ve contacted Brevo and they said that they have no responsibility over that issue.
Apparently, they need the number to be sent with a country code, but I’ve found no way to do that via Contact Form 7.
Could you please help with this issue?
Thanks in advance.