@kritikaargan: when you say “spam signups” are you referring to new user account sign ups? If so, Akismet doesn’t protect from user registrations – only comment and contact form spam.
Your contact form is using Contact Form 7, which does require some configuration to work with our API – you can find those instructions here:
https://contactform7.com/spam-filtering-with-akismet/
Also, can you look and see if those users are under Users -> All Users in your dashboard? If so, they’ve been added because you have the “anyone can register” option checked in your Settings -> General for “Membership” – on your WordPress login screen, the link to register can be seen here: https://d.pr/i/lCnXwJ
If you do not need to have open registration for your site, I recommend turning that off. Whatever you’re using for your online shop may have customer account registration separate from the WordPress membership settings.
I hope that clarifies things!