Secure Image CAPTCHA vs Google reCAPTCHA V2

I was using Secure Image Captcha for some time on my wordpress website. But I started to get spam messages coming from my blog’s contact form. So I have activated Google reCAPTCHA V2 (the one that uses images to tell a person from a robot).

In my Fast Secure Contact Form Settings, I have checked Google reCAPTCHA V2 and unchecked Secure Image CAPTCHA. (I thought that having both Captchas was too confusing for someone who wants to contact me thru my website).

However, I get both the Secure Image CAPTCHA and Google reCAPTCHA V2 still showing in my contact form.

How can I have only the Google reCAPTCHA V2, without the Secure Image CAPTCHA?

Please advise if you know how to get this done.