If you received the notification regarding the need of verifying your phone number when you tried to add funds, please follow these simple steps below:
In your CamModelDirectory account, go to Payments ⇒ Add funds.
Choose the country code from the drop-down menu and insert your phone number (as you will locally write it, without the country code). Don't forget to press Save. [Red square in the screenshot]
Press on "Send SMS with PIN code".
Insert the received PIN code in the PIN socket. [Red arrow in the screenshot]
Press Verify. Job done! Now you can add funds.